Objective：To research the effects of silencing tripartite motif containing 25（TRIM25） gene on cisplatin resistance and apop－tosis in cisplatin resistant lung cancer cell lines A549/DDP. Methods：Four types of short hairpin RNA were designed and prepared. The recombinant plasmids（pt1，pt2，pt3，pt4） were constructed respectively，which were transfected into A549/DDP cells using lipofectamine. Real-time PCR and Western blot were used to detect the inhibitory effects. The resistance of cisplatin to A549/DDP cells was detected by MTT assay. Cell apoptosis was tested by flow eytometry（FCM）. Results：The recombinant plasmid pt1 can inhibit mRNA and protein expression of TRIM25 specifically. MTT data showed that the cisplatin IC50 was decreased significantly in pt1 group than in pNC group（P=0.000） and control group（P=0.000） after the TRIM25 gene inhibition. According to the results of FCM，apoptotic cells was significantly decreased in pt1 group than in pNC group（P=0.005） and control group（P=0.004）. Conclusion：TRIM25 gene silencing in A549/DDP cells can effectively reduce cisplatin resistance and promote cells apoptosis.