The aim of this study was to investigate the effect of the p15 gene combined with Bcr-abl-specific siRNA and STI571 on the proliferation, cell cycle and apoptosis of K562 chronic myeloid leukemia cells. Using the gene sequence results, we amplified the p15 gene from normal peripheral blood by RT-PCR, and constructed a p15-pcDNA3.1 vector. The K562 cell line with G418 resistance was screened, synthesized and transfected for bcr-abl gene fusion point for 21-nt siRNA. In p15-pcDNA3.1-K562 cells, the growth rate was slower than that of the control K562 cells, G0/G1-phase was increased and S-phase was decreased significantly. In the siRNA group, bcr-abl fusion gene expression was significantly decreased in K562 cells accompanied by the downregulation of BCL-xL protein expression and G1-phase arrest. Cell survival rate was significantly decreased compared with the sole p15-K562 cell group and the sole RNA interference-K562 cell group. In the combination of p15-pcDNA3.1-K562 cells with STI571, the proportion of apoptosis was significantly increased and the cell survival rate was significantly decreased compared with the p15-K562 cell group and STI571-K562 cell group. siRNA at 30 pM combined with 0.5 μM STI571 promoted apoptosis compared with sole application. The p15 gene combined with siRNA had a synergistic effect on the inhibition of proliferation and the induction of apoptosis in K562 cells. Exogenous p15 protein expression combined with STI571 appeared to have a synergistic effect on proliferation inhibition and apoptosis induction in K562 cells. The combination of low-dose RNA interference with STI571 showed a synergistic effect in inducing apoptosis.