diff --git a/blocksuite/affine/components/src/rich-text/markdown/markdown-input.ts b/blocksuite/affine/components/src/rich-text/markdown/markdown-input.ts
index e08ec62d60..50a81b51c7 100644
--- a/blocksuite/affine/components/src/rich-text/markdown/markdown-input.ts
+++ b/blocksuite/affine/components/src/rich-text/markdown/markdown-input.ts
@@ -1,5 +1,9 @@
 import { CodeBlockModel, ParagraphBlockModel } from '@blocksuite/affine-model';
-import { isMarkdownPrefix, matchModels } from '@blocksuite/affine-shared/utils';
+import {
+  isHorizontalRuleMarkdown,
+  isMarkdownPrefix,
+  matchModels,
+} from '@blocksuite/affine-shared/utils';
 import { type BlockStdScope, TextSelection } from '@blocksuite/block-std';
 
 import { getInlineEditorByModel } from '../dom.js';
@@ -47,6 +51,10 @@ export function markdownInput(
     return toCode(std, model, prefixText, codeMatch[0].slice(3));
   }
 
+  if (isHorizontalRuleMarkdown(prefixText.trim())) {
+    return toDivider(std, model, prefixText);
+  }
+
   switch (prefixText.trim()) {
     case '[]':
     case '[ ]':
@@ -60,9 +68,6 @@ export function markdownInput(
     case '-':
     case '*':
       return toList(std, model, 'bulleted', prefixText);
-    case '***':
-    case '---':
-      return toDivider(std, model, prefixText);
     case '#':
       return toParagraph(std, model, 'h1', prefixText);
     case '##':
diff --git a/blocksuite/affine/shared/src/utils/string.ts b/blocksuite/affine/shared/src/utils/string.ts
index c369594acc..3136e467f2 100644
--- a/blocksuite/affine/shared/src/utils/string.ts
+++ b/blocksuite/affine/shared/src/utils/string.ts
@@ -76,10 +76,32 @@ export function substringMatchScore(name: string, query: string) {
 
 /**
  * Checks if the prefix is a markdown prefix.
- * Ex. 1. 2. 3. - * [] [ ] [x] # ## ### #### ##### ###### --- *** > ```
+ * Ex. 1. 2. 3. - * [] [ ] [x] # ## ### #### ##### ###### --- *** ___ > ```
  */
 export function isMarkdownPrefix(prefix: string) {
-  return !!prefix.match(
-    /^(\d+\.|-|\*|\[ ?\]|\[x\]|(#){1,6}|(-){3}|(\*){3}|>|```([a-zA-Z0-9]*))$/
+  return (
+    !!prefix.match(
+      /^(\d+\.|-|\*|\[ ?\]|\[x\]|(#){1,6}|>|```([a-zA-Z0-9]*))$/
+    ) || isHorizontalRuleMarkdown(prefix)
   );
 }
+
+/**
+ * Checks if the prefix is a valid markdown horizontal rule - https://www.markdownguide.org/basic-syntax/#horizontal-rules
+ * @param prefix - The string to check for horizontal rule syntax
+ * @returns boolean - True if the string represents a valid horizontal rule
+ *
+ * Valid horizontal rules:
+ * - Three or more consecutive hyphens (e.g., "---", "----")
+ * - Three or more consecutive asterisks (e.g., "***", "****")
+ * - Three or more consecutive underscores (e.g., "___", "____")
+ *
+ * Invalid examples:
+ * - Mixed characters (e.g., "--*", "-*-")
+ * - Less than three characters (e.g., "--", "**")
+ */
+export function isHorizontalRuleMarkdown(prefix: string) {
+  const horizontalRulePattern = /^(-{3,}|\*{3,}|_{3,})$/;
+
+  return !!prefix.match(horizontalRulePattern);
+}
diff --git a/blocksuite/tests-legacy/markdown.spec.ts b/blocksuite/tests-legacy/markdown.spec.ts
index 19989a5f29..7163b5f17f 100644
--- a/blocksuite/tests-legacy/markdown.spec.ts
+++ b/blocksuite/tests-legacy/markdown.spec.ts
@@ -175,18 +175,48 @@ test('markdown shortcut', async ({ page }) => {
   await undoByClick(page);
   await assertRichTexts(page, ['']);
 
+  // testing various horizontal dividers
   await waitNextFrame(page);
   await type(page, '--- ');
   await undoByClick(page);
   await assertRichTexts(page, ['--- ']);
   await undoByClick(page);
   await assertRichTexts(page, ['']);
+
   await waitNextFrame(page);
   await type(page, '*** ');
   await undoByClick(page);
   await assertRichTexts(page, ['*** ']);
   await undoByClick(page);
   await assertRichTexts(page, ['']);
+
+  await waitNextFrame(page);
+  await type(page, '___ ');
+  await undoByClick(page);
+  await assertRichTexts(page, ['___ ']);
+  await undoByClick(page);
+  await assertRichTexts(page, ['']);
+
+  await waitNextFrame(page);
+  await type(page, '------ ');
+  await undoByClick(page);
+  await assertRichTexts(page, ['------ ']);
+  await undoByClick(page);
+  await assertRichTexts(page, ['']);
+
+  await waitNextFrame(page);
+  await type(page, '****** ');
+  await undoByClick(page);
+  await assertRichTexts(page, ['****** ']);
+  await undoByClick(page);
+  await assertRichTexts(page, ['']);
+
+  await waitNextFrame(page);
+  await type(page, '______ ');
+  await undoByClick(page);
+  await assertRichTexts(page, ['______ ']);
+  await undoByClick(page);
+  await assertRichTexts(page, ['']);
 });
 
 test.describe('markdown inline-text', () => {