diff --git a/server/app/api/controller/CommunityController.php b/server/app/api/controller/CommunityController.php
index 03291ab..ab19971 100644
--- a/server/app/api/controller/CommunityController.php
+++ b/server/app/api/controller/CommunityController.php
@@ -84,9 +84,14 @@ class CommunityController extends BaseApiController
 
             if (!$isAuthor && !$isPurchased) {
                 $data['is_locked'] = true;
-                // 付费帖子只显示前20字符
-                if (mb_strlen($data['content']) > 20) {
-                    $data['content'] = mb_substr($data['content'], 0, 20) . '...';
+                // 付费帖子按配置展示免费预览，异常值回落到默认范围
+                $previewLength = (int) ($data['free_content_len'] ?? 100);
+                if ($previewLength <= 0) {
+                    $previewLength = 100;
+                }
+                $previewLength = max(20, min(500, $previewLength));
+                if (mb_strlen($data['content']) > $previewLength) {
+                    $data['content'] = mb_substr($data['content'], 0, $previewLength) . '...';
                 }
 
                 // 图片只保留第1张