Objective To investigate the mechanism by which JAK2 inhibitor Ruxolitinib affecting the proliferation and apoptosis of human erythroleukemia leukemia(HEL) cells. Methods The HEL cells were treated with Ruxolitinib at different concentrations (1, 5, 10, 50, 100, and 500 nmol/L). Then the cell viability was detected by CCK-8 assay; the cell apoptosis was detected by Hochest staining method, the cell cycle was detected by flow cytometry, the mitochondrial membrane potential was assessed by rhodamine 123 with flow cytometry, and the Cysteine aspartic acid specific protease (Caspase)-3/7 protein activities were tested by kits. Moreover, the expression of JAK2 mRNA was measured by RT-PCR and the protein expressions of p-JAK2,p-ERK,Bcl-2 and Bim were observed by Western blotting analysis. Results After treated with different concentrations of Ruxolitinib at 1 nmol/L, 5 nmol/L,10 nmol/L, 50 nmol/L,100 nmol/L, and 500 nmol/L for 48 h, the HEL cell viabilities were (97.0±4.4)%,(92.0±3.9)%,(88.0±3.7)%,(81.0±3.1)%,(64.0±2.9)%,and (38.0±2.2)%, respectively. The ratio of high blue cells was significantly increased after treatment with 100 nmol/L Ruxolitinib for 48 h compared with the control group ([49.21±1.80]% vs [10.02±1.40]%, P<0.05). Flow cytometry showed G₀/G₁ phase cell ratio was higher after HEL cells exposed to 100nmol/L Ruxolitinib for 48 h compared with the control group ([73.1±3.6]% vs [45.2±3.0]%). The mitochondrial membrane potential was significantly decreased and Caspase-3/7 activity was significantly enhanced by treatment with Ruxolitinib at different concentrations (1-500 nmol/L) for 12 h and 24 h. RT-PCR showed that Ruxolitinib decreased JAK2 mRNA expression in a concentration-dependent manner in HEL cells after 48 h treatment.Western blotting analysis showed that the protein expressions of p-JAK2,p-ERK and Bcl-2 were significantly lower and Bim protein was significantly higher than those of control group(P<0.01). Conclusion Ruxolitinib may induce HEL cell apoptosis via JAK2 and ERK 1/2 pathways.