diff --git a/doc/design/gan_api.md b/doc/design/gan_api.md
index f99d1e6540..2fb30432cb 100644
--- a/doc/design/gan_api.md
+++ b/doc/design/gan_api.md
@@ -29,7 +29,7 @@ In our GAN design, we wrap it as a user-friendly easily customized python API to
 
 <p align="center">
 <img src="./test.dot.png" width = "50%" align="center"/><br/>
-The overall running logic of GAN. The black solid arrows indicate the forward pass; the green dashed arrows indicate the backward pass of generator training; the red dashed arrows indicate the backward pass of the discriminator training. The BP pass of the green (red) arrow should only update the parameters in the green (red) boxes. The diamonds indicate the data providers.
+The overall running logic of GAN. The black solid arrows indicate the forward pass; the green dashed arrows indicate the backward pass of generator training; the red dashed arrows indicate the backward pass of the discriminator training. The BP pass of the green (red) arrow should only update the parameters in the green (red) boxes. The diamonds indicate the data providers. d\_loss and g\_loss mared in red and green are the two targets we would like to run.
 </p>
 
 
diff --git a/doc/design/test.dot b/doc/design/test.dot
new file mode 100644
index 0000000000..62c69b8fc8
--- /dev/null
+++ b/doc/design/test.dot
@@ -0,0 +1,35 @@
+
+digraph Test {
+    z -> generator -> G_img;
+    G_img -> discriminator -> D_f -> d_loss_f;
+    label0 -> d_loss_f -> d_loss;
+
+    img -> discriminator -> D_t -> d_loss_t;
+    label1 -> d_loss_t -> d_loss;
+
+    d_loss -> d_loss_t[color=red, style=dashed];
+    d_loss -> d_loss_f[color=red, style=dashed];
+    d_loss_t -> D_t[color=red, style=dashed];
+    d_loss_f -> D_f[color=red, style=dashed];
+    D_t -> discriminator[color=red, style=dashed];
+    D_f -> discriminator[color=red, style=dashed];
+
+    D_f -> g_loss;
+    label2 -> g_loss;
+
+    g_loss -> D_f[color=green, style=dashed];
+    D_f -> discriminator[color=green, style=dashed];
+    discriminator -> G_img[color=green, style=dashed];
+    G_img -> generator[color=green, style=dashed];
+
+    discriminator [color=red, shape=box];
+    generator [color=green, shape=box];
+    z [shape=diamond];
+    img [shape=diamond];
+    label0 [shape=diamond];
+    label1 [shape=diamond];
+    label2 [shape=diamond];
+
+    d_loss [color=red];
+    g_loss [color=green];
+}
diff --git a/doc/design/test.dot.png b/doc/design/test.dot.png
index 768e5cac4b..4e121a40b9 100644
Binary files a/doc/design/test.dot.png and b/doc/design/test.dot.png differ