Objective:To investigate the possible role of miR-181a/b in the development of cisplatin resistance in human lung cancer cell line A549/CDDP. Methods:Using quantitative real-time PCR analysis for miRNA and Western blot to detect the expression of miR-181a/b and anti-apoptotic protein BCL2,MCL1 and XIAP in cisplatin resistant human lung cancer cell line A549/cisplatin (CDDP) and its parental A549 cell,respectively. The luciferase reporter plasmids carried 3＇-untranslated region of BCL2,MCL1 and XIAP were constructed to testify the target genes of miR-181a/b,respectively. Using transient transfection of miR-181a/b to mimic the up-regulation of miR-181a/b in A549/CDDP cells and observe the effect of miR-181a/b on the expression level of BCL2,MCL1,XIAP and cisplatin resistance phenotype. Using flow cytometry to detect CDDP-induced apoptosis of the A549/CDDP cells after the transfection. Results:miR-181a/b was down-regulated in cisplatin-resistant human lung cancer cell line A549/CDDP,the down-regulation of miR-181a/b was concurrent with the over-expression of its targeted anti-apoptotic genes BCL2,MCL1 and XIAP in A549/CDDP cells,compared to the parental A549 cell line. The luciferase activity of BCL2,MCL1 and XIAP 3＇-untranslated region-based reporters construct in A549/CDDP cells suggested that BCL2,MCL1 and XIAP were the common target genes of the miR-181a/b. Over-expression of miR-181a/b sensitized A549/CDDP cells to CDDP. Overexpression of miR-181a/b also inhibited the expression of BCL2,MCL1 and XIAP and sensitized A549/CDDP cells to CDDP-induced apoptosis. Conclusion:miR-181a/b could enhance the sensitivity of cisplatin in human lung cancer cell line A549/CDDP,at least in part,by modulation of apoptosis via targeting multiple anti-apoptosis genes.