Abstract: ObjectiveTo explore the effects of different constituent ratio leinoleic acid(LA)/docosahexaenoic acid (DHA)on apoptosis of human gastric cancer cell line MKN-45.MethodsWith uniform design,the better constituen tratio for the inhibition of MKN-45 cell was scrceend.Then the best ratio was determined with randomized block design.The tumor volume,side-effect, and tumor weigh of tumor-bearing nude mice after treatment were observed.The morpho logical changes of tumor tissue were assessed by HE staining.ResultsThe LA/DHA constituen tratio of 1:3 showed maximum inhibition of the tumor cells.Six weeks after high concentration treatment, the mean tumor volume decreased by 21.97% and the mean tumor weigh by 18.09% with statistical significance compared with that of control group(P<0.05).The toxicit of the treatment was not obvious.Microscopic examination showed that there were massive areas of cytoclasis and apoptosis in the tumor tissue of the high concentration group and 5-FU group.ConclusionThe 1:3 constituen tratio of LA/DHA could induce the apoptosis of human gastric cancer cell line MKN-45.The high concentration of 1:3 constituent ratio treatment could also inhibit tumor in vivo without significant side-effect.