Abstract： Objective To investigate the effect of thalidomide on the proliferation and apoptosis in human pancreatic cancer cell SW1990 in vitro.Methods SW1990 cell line was treated with thalidomide at different concentrations (3.125,6.25,12.5,25,50,100,200 and 400 μg/ml) for 24,48,72 h,and then cell proliferation were evaluated by MTT.Cell cycle was determined by flow cytometry,apoptosis was determined by annexin V/PI fluos staining,Bcl-2,Bax protein expression and Bcl-2/Bax ratios were measured by Western Blot in vitro.Results Thalidomide inhibited the proliferation of SW1990 cells in a time and dosedependant manner.The proportion of G0/G1 phase of SW1990 cells with 200 μg/ml thalidomide treatment increased from (41.15 ± 2.23 ) ％ to (58.83 ± 2.33 ) ％,apoptosis rate increased from 2.6％ to 28.0％,the expression of Bax protein up-regulated from 0.17 ± 0.03 to 0.33 ± 0.04,the expression of Bcl-2 protein downregulated from 0.35 ± 0.02 to 0.17± 0.01,the ration of Bcl-2/Bax decreased from 2.17 ± 0.44 to 0.52 ±0.07.Conclusions Thalidomide can inhibit the proliferation of pancreatic cancer SW1990 cells by upregulating Bax,down-regulating Bcl-2,inducing cell apoptosis and cell Go/G1 phase arrest.