diff --git a/frontend/src/components/competition/ProjectSubmission.jsx b/frontend/src/components/competition/ProjectSubmission.jsx
index ee8da4e..8463eaf 100644
--- a/frontend/src/components/competition/ProjectSubmission.jsx
+++ b/frontend/src/components/competition/ProjectSubmission.jsx
@@ -248,14 +248,32 @@ const ProjectSubmission = ({ competitionId, initialValues, onCancel, onSuccess }
                 uploadProjectFile(formData)
                   .then(res => {
                     const imageUrl = res.data.file_url_display || res.data.file_url;
-                    updateProject(projectId, { cover_image_url: imageUrl })
+                    const currentValues = form.getFieldsValue();
+                    const updateData = {
+                      ...currentValues,
+                      cover_image_url: imageUrl,
+                    };
+                    if (updateData.cover_image_url && updateData.cover_image_url.startsWith('data:')) {
+                      delete updateData.cover_image_url;
+                    }
+                    console.log('Updating project with:', updateData);
+                    updateProject(projectId, updateData)
                       .then(() => {
                         form.setFieldsValue({ cover_image_url: imageUrl });
                         message.success('封面上传成功');
                       })
                       .catch(err => {
                         console.error('更新封面失败:', err);
-                        message.error(`更新封面失败: ${err.response?.data?.detail || err.message}`);
+                        const errorData = err.response?.data;
+                        let errorMsg = '更新失败';
+                        if (errorData) {
+                          if (typeof errorData === 'object') {
+                            errorMsg = Object.entries(errorData).map(([k, v]) => `${k}: ${Array.isArray(v) ? v.join(', ') : v}`).join('; ');
+                          } else {
+                            errorMsg = String(errorData);
+                          }
+                        }
+                        message.error(`更新封面失败: ${errorMsg}`);
                       });
                   })
                   .catch(err => {