Abstract: Objective To investigate the influence of methylation inhibitor of arsenic trioxide (As2O3) combined with 5-Aza-2′-deoxycytidine (5-aza-CdR) on the expression of JAK3, TYK2 and hematopoietic cell phosphatase SHP-1 in chronic myeloid leukemia cell line U937, and to explore the effects of the combination in leukemia pathogenesis. Methods 5-aza-CdR, As2O3 and the combined treatment were applied on U937 cells. As2O3 1 μmol/L and 5-aza-CdR 0.5μmol/L group, As2O3 2.5 μmol/L and 5-aza-CdR 1 μmol/L group, As2O3 5 μmol/L and 5-aza-CdR 2 μmol/L group and no chemical substances group were treated for 24, 48, 72 h, respectively. Then total cellular RNA was extracted. Real-time Quantitative PCR was used to detect the expression of JAK3, TYK2 and SHP-1. Results With the application of As2O3, 5-aza-CdR and the combination, SHP-1 mRNA expression in U937 cells was increased gradually, while JAK3 and TYK2 mRNA expression were decreased, in a dose- and time-dependent manner. SHP-1 was negatively correlated with JAK3 or TYK2. JAK3 was affected more obviously than TYK2. Conclusion (1) With the application of methylation inhibitor of As2O3 and 5-aza-CdR, the expression of SHP-1 was increased, while the expressions of JAK3 and TYK2 were decreased in a dose- and time- dependentmanner.(2)The reexpression of SHP-1 gene is related to its methylation and has a negative regulation role of JAK/STAT pathway.