Abstract: Objective: To investigate the combined effects of NK and T lymphocytes（NKTm cells） and cisplatin（DDP） on CFSE labeled human breast cancer cell line MDA-MB-231. Methods: CFSE/PI labeled cell line MDA-MB-231 was treated with NKTm cells or with NKTm cells and cisplatin.Cytotoxic activity was determined by MTT colorimetric assay and flow cytometry with specific antibodies. Results: The NKTm cells showed their cytotoxic effects on CFSE labeled cell line MDA-MB-231 in a concentration-dependent manner（P＜0.05）,The inhibition rate of NKTm cells（effector/target= 12.5:1） on CFSE labeled cell line MDA-MB-231 was lower than that of cisplatin（P＜0.05）.A synergistic effect of NKTm and cisplatin on CFSE labeled cell line MDA-MB-231 was also observed,The inhibition rate was higher in groups that received NKTm before cisplatin than in groups that received NKTm after cisplatin（P＜0.05）.IN groups that received NKTm first,the inhibition rate increased,but did not increase in groups that received cisplatin first,as demonstrated by MTT assay. Conclusion: NKTm cells have a highly direct cytotoxic effect on breast cancer cell line MDA-MB-231.NKTm cells and cisplatin have a synergetic effect on CFSE labeled cell line MDA-MB-231.