diff --git a/src/main/java/cc/ryanc/halo/model/dto/CategoryOutputDTO.java b/src/main/java/cc/ryanc/halo/model/dto/CategoryOutputDTO.java
index 9391095c1..f83a32161 100644
--- a/src/main/java/cc/ryanc/halo/model/dto/CategoryOutputDTO.java
+++ b/src/main/java/cc/ryanc/halo/model/dto/CategoryOutputDTO.java
@@ -13,6 +13,8 @@ import lombok.Data;
 @Data
 public class CategoryOutputDTO implements OutputConverter<CategoryOutputDTO, Category> {
 
+    private Integer id;
+
     private String name;
 
     private String slugName;
diff --git a/src/main/java/cc/ryanc/halo/model/params/CategoryParam.java b/src/main/java/cc/ryanc/halo/model/params/CategoryParam.java
new file mode 100644
index 000000000..1e2154637
--- /dev/null
+++ b/src/main/java/cc/ryanc/halo/model/params/CategoryParam.java
@@ -0,0 +1,58 @@
+package cc.ryanc.halo.model.params;
+
+import cc.ryanc.halo.model.dto.base.InputConverter;
+import cc.ryanc.halo.model.entity.Category;
+import cc.ryanc.halo.utils.SlugUtils;
+import lombok.Data;
+import org.apache.commons.lang3.StringUtils;
+
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.Size;
+
+/**
+ * Category param.
+ *
+ * @author johnniang
+ * @date 3/21/19
+ */
+@Data
+public class CategoryParam implements InputConverter<Category> {
+
+    /**
+     * 分类名称
+     */
+    @NotBlank(message = "Category name must not be blank")
+    @Size(max = 50, message = "Length of category name must not be more than {max}")
+    private String name;
+
+    /**
+     * 缩略名
+     */
+    @Size(max = 50, message = "Length of category slug name must not be more than {max}")
+    private String slugName;
+
+    /**
+     * 描述
+     */
+    @Size(max = 100, message = "Length of category description must not be more than {max}")
+    private String description;
+
+    /**
+     * 上级目录
+     */
+    private Integer parentId;
+
+    @Override
+    public Category convertTo() {
+        // Handle default value
+        if (StringUtils.isBlank(slugName)) {
+            slugName = SlugUtils.slugify(name);
+        }
+
+        if (parentId == null || parentId < 0) {
+            parentId = 0;
+        }
+
+        return InputConverter.super.convertTo();
+    }
+}
diff --git a/src/main/java/cc/ryanc/halo/model/vo/CategoryVO.java b/src/main/java/cc/ryanc/halo/model/vo/CategoryVO.java
new file mode 100644
index 000000000..32182a6dc
--- /dev/null
+++ b/src/main/java/cc/ryanc/halo/model/vo/CategoryVO.java
@@ -0,0 +1,18 @@
+package cc.ryanc.halo.model.vo;
+
+import cc.ryanc.halo.model.dto.CategoryOutputDTO;
+import lombok.Data;
+
+import java.util.List;
+
+/**
+ * Category vo.
+ *
+ * @author johnniang
+ * @date 3/21/19
+ */
+@Data
+public class CategoryVO extends CategoryOutputDTO {
+
+    private List<CategoryVO> children;
+}
diff --git a/src/main/java/cc/ryanc/halo/repository/CategoryRepository.java b/src/main/java/cc/ryanc/halo/repository/CategoryRepository.java
index ab6f545a5..87d4ca13a 100644
--- a/src/main/java/cc/ryanc/halo/repository/CategoryRepository.java
+++ b/src/main/java/cc/ryanc/halo/repository/CategoryRepository.java
@@ -2,6 +2,7 @@ package cc.ryanc.halo.repository;
 
 import cc.ryanc.halo.model.entity.Category;
 import cc.ryanc.halo.repository.base.BaseRepository;
+import org.springframework.lang.NonNull;
 
 /**
  * Category repository.
@@ -9,4 +10,20 @@ import cc.ryanc.halo.repository.base.BaseRepository;
  * @author johnniang
  */
 public interface CategoryRepository extends BaseRepository<Category, Integer> {
+
+    /**
+     * Counts by category name.
+     *
+     * @param name category name must not be blank
+     * @return the count
+     */
+    long countByName(@NonNull String name);
+
+    /**
+     * Counts by category id.
+     *
+     * @param id category id must not be null
+     * @return the count
+     */
+    long countById(@NonNull Integer id);
 }
diff --git a/src/main/java/cc/ryanc/halo/service/CategoryService.java b/src/main/java/cc/ryanc/halo/service/CategoryService.java
index 5830f3c45..528cca9fd 100755
--- a/src/main/java/cc/ryanc/halo/service/CategoryService.java
+++ b/src/main/java/cc/ryanc/halo/service/CategoryService.java
@@ -1,7 +1,12 @@
 package cc.ryanc.halo.service;
 
 import cc.ryanc.halo.model.entity.Category;
+import cc.ryanc.halo.model.vo.CategoryVO;
 import cc.ryanc.halo.service.base.CrudService;
+import org.springframework.data.domain.Sort;
+import org.springframework.lang.NonNull;
+
+import java.util.List;
 
 /**
  * Category service.
@@ -15,5 +20,15 @@ public interface CategoryService extends CrudService<Category, Integer> {
      *
      * @param id id
      */
-    void remove(Integer id);
+    @Deprecated
+    void remove(@NonNull Integer id);
+
+    /**
+     * Lists as category tree.
+     *
+     * @param sort sort info must not be null
+     * @return a category tree
+     */
+    @NonNull
+    List<CategoryVO> listAsTree(@NonNull Sort sort);
 }
diff --git a/src/main/java/cc/ryanc/halo/service/impl/CategoryServiceImpl.java b/src/main/java/cc/ryanc/halo/service/impl/CategoryServiceImpl.java
index 1983a431e..ac4d3f130 100644
--- a/src/main/java/cc/ryanc/halo/service/impl/CategoryServiceImpl.java
+++ b/src/main/java/cc/ryanc/halo/service/impl/CategoryServiceImpl.java
@@ -1,10 +1,22 @@
 package cc.ryanc.halo.service.impl;
 
+import cc.ryanc.halo.exception.AlreadyExistsException;
+import cc.ryanc.halo.exception.NotFoundException;
 import cc.ryanc.halo.model.entity.Category;
+import cc.ryanc.halo.model.vo.CategoryVO;
 import cc.ryanc.halo.repository.CategoryRepository;
 import cc.ryanc.halo.service.CategoryService;
 import cc.ryanc.halo.service.base.AbstractCrudService;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.data.domain.Sort;
+import org.springframework.lang.NonNull;
 import org.springframework.stereotype.Service;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
 
 /**
  * CategoryService implementation class
@@ -12,6 +24,7 @@ import org.springframework.stereotype.Service;
  * @author : RYAN0UP
  * @date : 2019-03-14
  */
+@Slf4j
 @Service
 public class CategoryServiceImpl extends AbstractCrudService<Category, Integer> implements CategoryService {
 
@@ -31,4 +44,107 @@ public class CategoryServiceImpl extends AbstractCrudService<Category, Integer>
     public void remove(Integer id) {
         // TODO 删除分类，以及和文章的对应关系
     }
+
+    @Override
+    public Category create(Category category) {
+        Assert.notNull(category, "Category to create must not be null");
+
+        // Check the category name
+        long count = categoryRepository.countByName(category.getName());
+
+        if (count > 0) {
+            log.error("Category has exist already: [{}]", category);
+            throw new AlreadyExistsException("The category has exist already");
+        }
+
+        // Check parent id
+        if (category.getParentId() > 0) {
+            count = categoryRepository.countById(category.getParentId());
+
+            if (count == 0) {
+                log.error("Parent category with id: [{}] was not found, category: [{}]", category.getParentId(), category);
+                throw new NotFoundException("Parent category with id = " + category.getParentId() + " was not found");
+            }
+        }
+
+        // Create it
+        return super.create(category);
+    }
+
+    @Override
+    public List<CategoryVO> listAsTree(Sort sort) {
+        Assert.notNull(sort, "Sort info must not be null");
+
+        // List all category
+        List<Category> categories = listAll(sort);
+
+        if (CollectionUtils.isEmpty(categories)) {
+            return Collections.emptyList();
+        }
+
+        // Create top category
+        CategoryVO topLevelCategory = createTopLevelCategory();
+
+        // Concrete the tree
+        concreteTree(topLevelCategory, categories);
+
+        return topLevelCategory.getChildren();
+    }
+
+    /**
+     * Concrete category tree.
+     *
+     * @param parentCategory parent category vo must not be null
+     * @param categories     a list of category
+     */
+    private void concreteTree(CategoryVO parentCategory, List<Category> categories) {
+        Assert.notNull(parentCategory, "Parent category must not be null");
+
+        if (CollectionUtils.isEmpty(categories)) {
+            return;
+        }
+
+        // Create children container for removing after
+        List<Category> children = new LinkedList<>();
+
+        categories.forEach(category -> {
+            if (parentCategory.getId().equals(category.getParentId())) {
+                // Save child category
+                children.add(category);
+
+                // Convert to child category vo
+                CategoryVO child = new CategoryVO().convertFrom(category);
+
+                // Init children if absent
+                if (parentCategory.getChildren() == null) {
+                    parentCategory.setChildren(new LinkedList<>());
+                }
+                parentCategory.getChildren().add(child);
+            }
+        });
+
+        // Remove all child categories
+        categories.removeAll(children);
+
+        // Foreach children vos
+        if (!CollectionUtils.isEmpty(parentCategory.getChildren())) {
+            parentCategory.getChildren().forEach(childCategory -> concreteTree(childCategory, categories));
+        }
+    }
+
+    /**
+     * Creates a top level category.
+     *
+     * @return top level category with id 0
+     */
+    @NonNull
+    private CategoryVO createTopLevelCategory() {
+        CategoryVO topCategory = new CategoryVO();
+        // Set default value
+        topCategory.setId(0);
+        topCategory.setChildren(new LinkedList<>());
+        topCategory.setParentId(-1);
+
+        return topCategory;
+    }
 }
diff --git a/src/main/java/cc/ryanc/halo/web/controller/admin/api/CategoryController.java b/src/main/java/cc/ryanc/halo/web/controller/admin/api/CategoryController.java
new file mode 100644
index 000000000..e4108d62e
--- /dev/null
+++ b/src/main/java/cc/ryanc/halo/web/controller/admin/api/CategoryController.java
@@ -0,0 +1,48 @@
+package cc.ryanc.halo.web.controller.admin.api;
+
+import cc.ryanc.halo.model.dto.CategoryOutputDTO;
+import cc.ryanc.halo.model.entity.Category;
+import cc.ryanc.halo.model.params.CategoryParam;
+import cc.ryanc.halo.model.vo.CategoryVO;
+import cc.ryanc.halo.service.CategoryService;
+import io.swagger.annotations.ApiOperation;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.web.SortDefault;
+import org.springframework.web.bind.annotation.*;
+
+import javax.validation.Valid;
+import java.util.List;
+
+import static org.springframework.data.domain.Sort.Direction.ASC;
+
+/**
+ * Category controller.
+ *
+ * @author johnniang
+ * @date 3/21/19
+ */
+@RestController
+@RequestMapping("/admin/api/categories")
+public class CategoryController {
+
+    private final CategoryService categoryService;
+
+    public CategoryController(CategoryService categoryService) {
+        this.categoryService = categoryService;
+    }
+
+    @GetMapping("tree")
+    @ApiOperation("List as category tree")
+    public List<CategoryVO> listAsTree(@SortDefault(sort = "name", direction = ASC) Sort sort) {
+        return categoryService.listAsTree(sort);
+    }
+
+    @PostMapping
+    public CategoryOutputDTO createBy(@Valid @RequestBody CategoryParam categoryParam) {
+        // Convert to category
+        Category category = categoryParam.convertTo();
+
+        // Save it
+        return new CategoryOutputDTO().convertFrom(categoryService.create(category));
+    }
+}
diff --git a/src/main/java/cc/ryanc/halo/web/controller/admin/api/PostController.java b/src/main/java/cc/ryanc/halo/web/controller/admin/api/PostController.java
index 5e9021196..e04c40645 100644
--- a/src/main/java/cc/ryanc/halo/web/controller/admin/api/PostController.java
+++ b/src/main/java/cc/ryanc/halo/web/controller/admin/api/PostController.java
@@ -38,7 +38,7 @@ public class PostController {
     }
 
     @GetMapping("status/{status}")
-    @ApiOperation("")
+    @ApiOperation("Gets a page of post by post status")
     public Page<PostSimpleOutputDTO> pageByStatus(@PathVariable(name = "status") PostStatus status,
                                                   @PageableDefault(sort = "updateTime", direction = DESC) Pageable pageable) {
         return postService.pageSimpleDtoByStatus(status, PostType.POST, pageable);