bcr /abl RNAi lentivirus vector was constructed and used to transfect K562 cells( the first human immortalised myelogenous leukemia line to be established),and the stable transfectants were selected. RNAi efficiency was assessed by Real-time PCR and Western blotting. The viability of the K562 cells was detected by CCK-8 assay and clonogenic assay. The results showed that bcr / abl RNAi significantly down regulates the amount of bcr / abl mRNA and P210bcr / ablfusion protein,and inhibits the proliferation of the K562 cells. The method of RNAi targeting bcr / abl fusion gene highlights a new way of chronic myelogenous leukemia treatment.