To explore a new way to treat CML, inhibitory effect of small interfering RNA (SiRNA) on bcr-abl fusion gene expression of K562 cell line was studied. SiRNA for bcr-abl gene was designed and transfected into K562 cells, bcr-abl gene expression was tested by RT-PCR. The results showed that bcr-abl gene expression was inhibited by using siRNA in dose-dependent manner and reduced to 19.9% and 26.6% of the control at 24 and 48 hours after transfection with 0.2 micro g siRNA respectively. K562 cells proliferation was suppressed finally, but bcr-abl gene expression restored at 72 hours. In conclusion, anti-bcr-abl siRNA can effectively inhibit bcr-abl gene expression of K562 cell line.