diff --git a/src/main/java/cc/ryanc/halo/model/params/CommentParam.java b/src/main/java/cc/ryanc/halo/model/params/CommentParam.java
index a28ab5a8f..89b55b64d 100644
--- a/src/main/java/cc/ryanc/halo/model/params/CommentParam.java
+++ b/src/main/java/cc/ryanc/halo/model/params/CommentParam.java
@@ -10,6 +10,8 @@ import javax.validation.constraints.NotBlank;
 import javax.validation.constraints.Size;
 
 /**
+ * Comment param.
+ *
  * @author johnniang
  * @date 3/22/19
  */
@@ -32,9 +34,6 @@ public class CommentParam implements InputConverter<Comment> {
     @Size(max = 1023, message = "Length of comment content must not be more than {max}")
     private String content;
 
-    @Size(max = 512, message = "Length of comment user agent must not be more than {max}")
-    private String userAgent;
-
     @Min(value = 1, message = "Post id must not be less than {value}")
     private Integer postId;
 
diff --git a/src/main/java/cc/ryanc/halo/service/CommentService.java b/src/main/java/cc/ryanc/halo/service/CommentService.java
index 5f518df85..6a8f6d19b 100644
--- a/src/main/java/cc/ryanc/halo/service/CommentService.java
+++ b/src/main/java/cc/ryanc/halo/service/CommentService.java
@@ -2,7 +2,6 @@ package cc.ryanc.halo.service;
 
 import cc.ryanc.halo.model.entity.Comment;
 import cc.ryanc.halo.model.enums.CommentStatus;
-import cc.ryanc.halo.model.params.CommentParam;
 import cc.ryanc.halo.model.vo.CommentListVO;
 import cc.ryanc.halo.service.base.CrudService;
 import org.springframework.data.domain.Page;
@@ -69,10 +68,10 @@ public interface CommentService extends CrudService<Comment, Long> {
     /**
      * Creates a comment by comment param.
      *
-     * @param commentParam comment param must not be null and should be validated
-     * @param request      http servlet request must not be null
+     * @param comment comment must not be null
+     * @param request http servlet request must not be null
      * @return created comment
      */
     @NonNull
-    Comment createBy(@NonNull CommentParam commentParam, @NonNull HttpServletRequest request);
+    Comment createBy(@NonNull Comment comment, @NonNull HttpServletRequest request);
 }
diff --git a/src/main/java/cc/ryanc/halo/service/impl/CommentServiceImpl.java b/src/main/java/cc/ryanc/halo/service/impl/CommentServiceImpl.java
index 397a9ff54..3e80090f4 100644
--- a/src/main/java/cc/ryanc/halo/service/impl/CommentServiceImpl.java
+++ b/src/main/java/cc/ryanc/halo/service/impl/CommentServiceImpl.java
@@ -1,12 +1,10 @@
 package cc.ryanc.halo.service.impl;
 
-import cc.ryanc.halo.exception.NotFoundException;
 import cc.ryanc.halo.model.dto.post.PostMinimalOutputDTO;
 import cc.ryanc.halo.model.entity.Comment;
 import cc.ryanc.halo.model.entity.Post;
 import cc.ryanc.halo.model.enums.BlogProperties;
 import cc.ryanc.halo.model.enums.CommentStatus;
-import cc.ryanc.halo.model.params.CommentParam;
 import cc.ryanc.halo.model.projection.CommentCountProjection;
 import cc.ryanc.halo.model.vo.CommentListVO;
 import cc.ryanc.halo.repository.CommentRepository;
@@ -22,6 +20,7 @@ import cn.hutool.extra.servlet.ServletUtil;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.StringUtils;
 import org.springframework.data.domain.*;
+import org.springframework.http.HttpHeaders;
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Service;
@@ -99,27 +98,14 @@ public class CommentServiceImpl extends AbstractCrudService<Comment, Long> imple
     }
 
     @Override
-    public Comment createBy(CommentParam commentParam, HttpServletRequest request) {
-        Assert.notNull(commentParam, "Comment param must not be null");
+    public Comment createBy(Comment comment, HttpServletRequest request) {
+        Assert.notNull(comment, "Comment must not be null");
         Assert.notNull(request, "Http servlet request must not be null");
 
-        if (!postRepository.existsById(commentParam.getPostId())) {
-            // Post id must exist
-            log.error("Post: [{}] was not found", commentParam.getPostId());
-            throw new NotFoundException("The post was not found").setErrorData(commentParam.getPostId());
-        }
-
-        if (commentParam.getParentId() != null && commentParam.getParentId() > 0) {
-            // Validate the comment parent id
-            mustExistById(commentParam.getParentId());
-        }
-
-        // Convert to comment
-        Comment comment = commentParam.convertTo();
-
         // Set some default value
         comment.setContent(OwoUtil.parseOwo(formatContent(comment.getContent())));
         comment.setIpAddress(ServletUtil.getClientIP(request));
+        comment.setUserAgent(ServletUtil.getHeaderIgnoreCase(request, HttpHeaders.USER_AGENT));
         // TODO Check user login status and set this field
         comment.setIsAdmin(false);
         comment.setAuthor(HtmlUtils.htmlEscape(comment.getAuthor()));
diff --git a/src/main/java/cc/ryanc/halo/web/controller/admin/api/CommentController.java b/src/main/java/cc/ryanc/halo/web/controller/admin/api/CommentController.java
index 0e29c6e98..19885a51b 100644
--- a/src/main/java/cc/ryanc/halo/web/controller/admin/api/CommentController.java
+++ b/src/main/java/cc/ryanc/halo/web/controller/admin/api/CommentController.java
@@ -57,7 +57,15 @@ public class CommentController {
 
     @PostMapping
     public CommentOutputDTO createBy(@Valid @RequestBody CommentParam commentParam, HttpServletRequest request) {
-        return new CommentOutputDTO().convertFrom(commentService.createBy(commentParam, request));
+        // Check post id
+        postService.mustExistById(commentParam.getPostId());
+
+        // Check parent id
+        if (commentParam.getParentId() != null && commentParam.getParentId() > 0) {
+            commentService.mustExistById(commentParam.getParentId());
+        }
+
+        return new CommentOutputDTO().convertFrom(commentService.createBy(commentParam.convertTo(), request));
     }
 
 }