diff --git a/backend/app/generator/README.md b/backend/app/generator/README.md
index ae9677b3..91aaeaa3 100644
--- a/backend/app/generator/README.md
+++ b/backend/app/generator/README.md
@@ -29,7 +29,7 @@
 
 1. 通过创建业务接口手动添加一项业务数据
 2. 通过模型创建接口手动添加模型列
-3. 访问 `preview`，`generate`，`download`接口，生成相应后端代码
+3. 访问 `preview`（预览），`generate`（磁盘写入），`download`（下载）接口，执行后端代码生成相应工作
 
 ### S. 自动模式
 
@@ -37,4 +37,4 @@
 
 1. 访问 `tables` 接口，获取数据库表名列表
 2. 通过 `import` 接口，导入数据库已有的数据库表数据，将自动创建业务表数据和模型表数据
-3. 访问 `preview`，`generate`，`download`接口，生成相应后端代码
+3. 访问 `preview`（预览），`generate`（磁盘写入），`download`（下载）接口，执行后端代码生成相应工作
diff --git a/backend/app/generator/service/gen_service.py b/backend/app/generator/service/gen_service.py
index cd922012..e82f3aef 100644
--- a/backend/app/generator/service/gen_service.py
+++ b/backend/app/generator/service/gen_service.py
@@ -47,6 +47,9 @@ class GenService:
             table_info = await gen_dao.get_table(db, table_name)
             if not table_info:
                 raise errors.NotFoundError(msg='数据库表不存在')
+            business_info = await gen_business_dao.get_by_name(db, table_name)
+            if business_info:
+                raise errors.ForbiddenError(msg='已存在相同数据库表业务')
             table_name = table_info[0]
             business_data = {
                 'app_name': app,
@@ -122,15 +125,15 @@ class GenService:
             business = await gen_business_dao.get(db, pk)
             if not business:
                 raise errors.NotFoundError(msg='业务不存在')
-        bio = io.BytesIO()
-        zf = zipfile.ZipFile(bio, 'w')
-        tpl_code_map = await self.render_tpl_code(business=business)
-        for tpl_path, code in tpl_code_map.items():
-            new_code_path = gen_template.get_code_gen_path(tpl_path, business)
-            zf.writestr(new_code_path, code)
-        zf.close()
-        bio.seek(0)
-        return bio
+            bio = io.BytesIO()
+            zf = zipfile.ZipFile(bio, 'w')
+            tpl_code_map = await self.render_tpl_code(business=business)
+            for tpl_path, code in tpl_code_map.items():
+                new_code_path = gen_template.get_code_gen_path(tpl_path, business)
+                zf.writestr(new_code_path, code)
+            zf.close()
+            bio.seek(0)
+            return bio
 
 
 gen_service = GenService()
diff --git a/backend/templates/py/model.jinja b/backend/templates/py/model.jinja
index 20acda47..e4445f5a 100644
--- a/backend/templates/py/model.jinja
+++ b/backend/templates/py/model.jinja
@@ -12,5 +12,5 @@ class {{ table_name_class }}({% if have_datetime_column %}Base{% else %}MappedBa
 
     id: Mapped[id_key] = mapped_column(init=False)
     {% for model in models %}
-    {{ model.name }}: {% if model.is_nullable %}Mapped[{{ model.type | None }}]{% else %}Mapped[{{ model.type }}]{% endif %} = mapped_column({% if model.type == 'str' %}{{ model_type_mapping.get(model.type) }}({{ model.length }}){% else %}{{ model_type_mapping.get(model.type) or model.type}}(){% endif %}, default={{ model.default }}, sort_order={{ model.sort }}, comment={{ model.comment }})
+    {{ model.name }}: {% if model.is_nullable %}Mapped[{{ model.type }} | None]{% else %}Mapped[{{ model.type }}]{% endif %} = mapped_column({% if model.type == 'str' and model.length != 0 %}{{ model_type_mapping.get(model.type) }}({{ model.length }}){% else %}{{ model_type_mapping.get(model.type) or model.type}}(){% endif %}, default={{ model.default }}, sort_order={{ model.sort }}, comment={{ model.comment }})
     {% endfor %}