diff --git a/alembic/versions/20251215_1707_180e63a9c83a_add_first_byte_time_ms_to_usage_table.py b/alembic/versions/20251215_1707_180e63a9c83a_add_first_byte_time_ms_to_usage_table.py
new file mode 100644
index 0000000..3d93a13
--- /dev/null
+++ b/alembic/versions/20251215_1707_180e63a9c83a_add_first_byte_time_ms_to_usage_table.py
@@ -0,0 +1,28 @@
+"""add first_byte_time_ms to usage table
+
+Revision ID: 180e63a9c83a
+Revises: e9b3d63f0cbf
+Create Date: 2025-12-15 17:07:44.631032+00:00
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '180e63a9c83a'
+down_revision = 'e9b3d63f0cbf'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    """应用迁移：升级到新版本"""
+    # 添加首字时间字段到 usage 表
+    op.add_column('usage', sa.Column('first_byte_time_ms', sa.Integer(), nullable=True))
+
+
+def downgrade() -> None:
+    """回滚迁移：降级到旧版本"""
+    # 删除首字时间字段
+    op.drop_column('usage', 'first_byte_time_ms')
diff --git a/src/models/database.py b/src/models/database.py
index 98b231d..1406d03 100644
--- a/src/models/database.py
+++ b/src/models/database.py
@@ -307,7 +307,8 @@ class Usage(Base):
     is_stream = Column(Boolean, default=False)  # 是否为流式请求
     status_code = Column(Integer)
     error_message = Column(Text, nullable=True)
-    response_time_ms = Column(Integer)  # 响应时间（毫秒）
+    response_time_ms = Column(Integer)  # 总响应时间（毫秒）
+    first_byte_time_ms = Column(Integer, nullable=True)  # 首字时间/TTFB（毫秒）
 
     # 请求状态追踪
     # pending: 请求开始处理中