diff --git a/zt-module-infra/zt-module-infra-server/src/main/java/com/zt/plat/module/infra/controller/admin/file/FileController.java b/zt-module-infra/zt-module-infra-server/src/main/java/com/zt/plat/module/infra/controller/admin/file/FileController.java
index f33232bc..17ec1e54 100644
--- a/zt-module-infra/zt-module-infra-server/src/main/java/com/zt/plat/module/infra/controller/admin/file/FileController.java
+++ b/zt-module-infra/zt-module-infra-server/src/main/java/com/zt/plat/module/infra/controller/admin/file/FileController.java
@@ -270,18 +270,32 @@ public class FileController {
     }
 
     private String buildPublicBaseUrl(HttpServletRequest request) {
-        if (previewBaseUrl != null && !previewBaseUrl.isBlank()) {
-            return previewBaseUrl.endsWith("/")
-                    ? previewBaseUrl.substring(0, previewBaseUrl.length() - 1)
-                    : previewBaseUrl;
+        // 1. 优先使用配置（必须是合法 http(s)）
+        if (previewBaseUrl != null) {
+            String v = previewBaseUrl.trim();
+            if (!v.isEmpty() && (v.startsWith("http://") || v.startsWith("https://"))) {
+                return v.endsWith("/") ? v.substring(0, v.length() - 1) : v;
+            }
         }
-        // 兜底：从请求推断
-        String scheme = request.getHeader("X-Forwarded-Proto");
-        if (scheme == null) scheme = request.getScheme();
 
+        // 2. 从请求头推断 scheme（注意：多级代理会是 "http,http"）
+        String scheme = request.getHeader("X-Forwarded-Proto");
+        if (scheme == null || scheme.isBlank()) {
+            scheme = request.getScheme();
+        } else {
+            scheme = scheme.split(",")[0].trim();
+        }
+
+        // 3. 从请求头推断 host（同样可能是多值）
         String host = request.getHeader("X-Forwarded-Host");
-        if (host == null) host = request.getHeader("Host");
-        if (host == null) host = request.getServerName() + ":" + request.getServerPort();
+        if (host == null || host.isBlank()) {
+            host = request.getHeader("Host");
+        }
+        if (host == null || host.isBlank()) {
+            host = request.getServerName() + ":" + request.getServerPort();
+        } else {
+            host = host.split(",")[0].trim();
+        }
 
         return scheme + "://" + host;
     }