Objective To evaluate of impact of thalidomide on CD4 +CD25 +T lymphocytes in patients with acute myeloid leukemia and its clinical curative effect.Methods 71 cases of patients with AML were randomly divided into the control group and the experiment group, and 31 healthy people were selected to be the normal group.The experiment group and the control group patients were treated with the same chemotherapy, the experiment group was treated with thalidomide.The levels of CD4 +CD25 +T lymphocyte, CD3 +T lymphocyte, CD4 +T lymphocyte, CD8 +T lymphocyte, ratio of CD4 +/CD8 +and NK cells were detected at before treatment, 10 to 14d after treatment, complete remission 6 months follow-up.In normal group, the same index was detected before and after chemotherapy, and 10-14 d.The clinical curative effect of the experiment group and the control group were observed.Results The effective rate of the experiment group was higher than of the control group(P<0.05); The levels of CD4 +CD25 +T lymphocyte in the experiment group and control group were significantly higher than in the normal group(P<0.05), the two groups decreased compared with the control group, the level of CD4 +CD25 +T lymphocyte in the experiment group was significantly decreased(P<0.05).And with thalidomide treatment, the experiment group in the CD3 +T lymphocytes, CD4 +T lymphocytes and ratio of CD4 +/CD8 +, NK cells were significantly higher than the control group ( P<0.05 ) .Conclusion Thalidomide can improve both the immunity cell function and the clinical efficiency in patients with AML.The mechanism is related to reduce the level of CD4 +CD25 +T lymphocyte.