This study was aimed to explore the inhibitory effect of triptolide on proliferation and inducing apoptosis effect of K562/G01 cells and their possible mechanism. MTT assay was used to detect the effect of imatinib or triptolide alone and their combination on K562/G01 proliferation; the cell cycle, apoptosis rate, P-gp protein expression were detected by flow cytometry (FCM); the expression of P-gp was assessed by Western blot; the BCR/ABL gene expression was assayed by real time quantitative PCR. The results showed that triptolide could enhance the effect of imatinib on proliferation inhibition and apoptosis of K562/G01, arrested the cell cycle in G1 phase, down-regulated the expression of BCR/ABL gene and P-gp protein. It is concluded that triptolide induces K562/G01 cell proliferation inhibition and apoptosis, the mechanism may be related to cell cycle arrest, decrease of P-gp protein expression, inhibition of BCR/ABL gene expression.