diff --git a/source/_static/code/zh/basic/example/numpy_manual_grad.py b/source/_static/code/zh/basic/example/numpy_manual_grad.py
index f874901e..de868967 100644
--- a/source/_static/code/zh/basic/example/numpy_manual_grad.py
+++ b/source/_static/code/zh/basic/example/numpy_manual_grad.py
@@ -13,9 +13,9 @@
 for e in range(num_epoch):
     # 手动计算损失函数关于自变量（模型参数）的梯度
     y_pred = a * X + b
-    grad_a, grad_b = (y_pred - y).dot(X), (y_pred - y).sum()
+    grad_a, grad_b = 2*(y_pred - y).dot(X), 2*(y_pred - y).sum()
 
     # 更新参数
     a, b = a - learning_rate * grad_a, b - learning_rate * grad_b
 
-print(a, b)
\ No newline at end of file
+print(a, b)