Abstract: To determine the effects of celastrol on the proliferation and apoptosis of cell lines HL-60 and Jurkat in human leukemia. Human leukemia cell lines were treated with celastrol at different concentrations. The inhibitory rate of cell proliferation was detected by MTT assay; the apoptosis rate was detected by AnnexinV-FITC/PI double staining; cell cycle was observed by PI staining; cell morphology was observed by transmission electron microscope(TEM). Cell proliferation was inhibited by celastrol, with IC₅₀ of(0. 46±1. 05)μmol/L and(0. 88±1. 13)μmol/L at 24 h. Celastrol induced cell apoptosis in a dose-dependent manner. The cell cycle distribution of G₁ phase rate increased, S phase rate decreased(P< 0. 05)with typical cell apoptosis-induced morphological changes. Results showed that celastrol could significantly inhibit cell proliferation and induce apoptosis in human leukemia cell lines of HL-60 and Jurkat.