diff --git a/src/lib/markdown.ts b/src/lib/markdown.ts
index cc0da34..22960bb 100644
--- a/src/lib/markdown.ts
+++ b/src/lib/markdown.ts
@@ -29,6 +29,35 @@ const allowed_langs = [
   'mermaid',
 ]
 
+/**
+ * KaTeX 渲染结果修改。
+ *
+ * 让 KaTeX 的公式可复制。
+ */
+
+function setupKatexCopy(md: MarkdownIt) {
+  const defaultInline = md.renderer.rules.math_inline!
+  const defaultBlock = md.renderer.rules.math_block!
+
+  md.renderer.rules.math_inline = (tokens, idx, options, env, self) => {
+    const content = tokens[idx].content
+    const rendered = defaultInline(tokens, idx, options, env, self)
+
+    return `<span class="katex-wrapper inline" data-code="${encodeURIComponent(content)}">${rendered}</span>`
+  }
+
+  md.renderer.rules.math_block = (tokens, idx, options, env, self) => {
+    const content = tokens[idx].content
+    const rendered = defaultBlock(tokens, idx, options, env, self)
+    return `
+      <div class="katex-wrapper block" data-code="${encodeURIComponent(content)}">${rendered}
+        <button class="copy-katex" title="Copy LaTeX">
+复制
+        </button>
+      </div>`
+  }
+}
+
 /**
  * Markdown 渲染函数。
  *
@@ -59,6 +88,7 @@ export async function renderMarkdown(content: string): Promise<string> {
   })
 
   md.use(mdKatex)
+  setupKatexCopy(md)
 
   return md.render(content)
 }