diff --git a/src/Identity/EvidenceService.php b/src/Identity/EvidenceService.php
index cbc67f29..b696d4cc 100644
--- a/src/Identity/EvidenceService.php
+++ b/src/Identity/EvidenceService.php
@@ -63,7 +63,13 @@ final class EvidenceService {
             ], 0, __('身份认证证明材料', 'aksrt'));
             if (is_wp_error($id)) {
                 $this->delete($ids);
-                return new \WP_Error('aksrt_identity_upload_write', __('证明材料写入失败', 'aksrt'));
+                // 透传 WordPress 的真实原因（例如后台格式限制里禁止了该格式），
+                // 否则前端只会看到一句含义不明的“写入失败”。
+                $reason = wp_strip_all_tags(trim((string) $id->get_error_message()));
+                return new \WP_Error(
+                    'aksrt_identity_upload_write',
+                    $reason !== '' ? $reason : __('证明材料写入失败', 'aksrt')
+                );
             }
             $id = (int) $id;
             wp_update_post(['ID' => $id, 'post_author' => $user_id, 'post_status' => 'private']);