I changed the dataset(source data count:20000, target data count:2100) Result: source only: mydata set: Average loss: 2.1571, Accuracy: 1311/2100 (62.00%) domain adaptation: mydata set: Average loss: 4.5971, Accuracy: 327/2100 (15.00%) Because GPU has small memory , I set batchsize=16,Is this batchsize problem? Thank you for your help!