Objective: To explore whether Nilotinib (AMN107) and arsenic trioxide (ATO) had synergistic effect, to provide theoretical basis for the new treatment of chronic myelocytic leukemia. Methods: K562 cells were cultivated in vitro, treated with AMN107, ATO or both; Cell proliferation of K562 cells were evaluated by using a MTT assay. Cell apoptosis of K562 cells were examined by using Flow cytometry. Cell cycle of K562 cells were anlysised by using Flow cytometry. The expression levels of BCR-ABL fusion genes of K562 cells were analyzed by using PT-PCR. Results: MTT shows that both of the AMN107 and ATO can inhibit the growth of the cells of K562, the combination of the two drugs was better than single one. Flow cytometry detected the cell apoptosis (%), AMN107 (10 umol/L) was 74.86 ± 1.86, ATO (5 umol/L) was 24.12 ± 2.03, the combination were 84.60 ± 1.80. RT-PCR shows that the combination group treated with the K562 cells after 24 h, 48 h, 72 h, the RQ of BCR/ABL were: 0.51 ± 0.00, 0.46 ± 0.00, 0.37 ± 0.02. The results were better than single one (P < 0.05).