To explore the relationship between microRNA and drug resistance in leukemia treatment by screening and identifying the microRNAs which differentially express in K562 cell line and its adriamycin resistant cells-K562/A02 cell line.The drug resistance potency of K562/A02 cells was evaluated by MTT assay. P-gp expression of K562 and K562/A02 cells were detected by flow cytometry (FCM). The differentially expressed microRNAs in K562 and K562/A02 cells were analyzed by microarray technique and Real Time RT-PCR.The resistance to adriamycin (ADM) of K562/A02 cells was 180 fold greater than that of K562 cells. P-gp expression rate of K562 and K562/A02 cells was 0.2% and 86%, respectively. Twenty-two microRNAs expressed differentially in K562 and K562/A02 cells (P < 0.01). As compared to K562 cells, expressions of miR-221, miR-155 and miR-451 were up-regulated by more than two fold, while expression of miR-98, miR-181a, let-7f, let-7g, miR-424 and miR-563 down-regulated by more than two fold in K562/A02 cells. The results of real time RT-PCR were consistent with that of microarray. Of note, differential expressions of miR-451, miR-155, miR-221, let-7f and miR-424 were remarkable.K562/A02 cells show a different microRNA expression profile as compared to its parental K562 cells, suggesting microRNAs including miR-221, miR-155, miR-451, let-7f and miR-424 may be involved in the mechanism of drug resistance in leukemia. These differentially expressed microRNAs provide potential novel targets for overcoming drug-resistance.