Abstract: Objective 　To study effect of one amino acid mutation in an anti-cd20 antibody fragment Fab′on ROS, Caspase-3 in Blymphoma Raji cells. Methods 　MTT was used to observe the effect of anti-CD20 Fab′on Raji cell growth ;morphologic change through microscope were used to assay apoptosiss induced by anti-CD20 Fab′,ROS labeled with DCFH-DA in cells was processed on FACS, Caspase-3 gene expression local change in Raji cells FACS using Western-blottong. Results 　The result of MTT indicated that the growth of Raji cell was inhibited by chimeric anti-CD20 antibody f ragment Fab′,the apoptotic bodies were observed, ROS and Casepase-3 level in Raji cell was increased by anti-CD20 Fab′. Conclusion 　The increasing of ROS, Caspase-3 level is important in the apoptosis of Raji cell induced by anti-CD20 Fab′.