Multidrug resistance (MDR) is one of the primary causes of failure in chemotherapy of leukemia. It is very difficult in clinical therapy. In comparison with reverse RNA, RNAi technique is inexpensive, high effective, high specific, simple and fast. It is a new way for the study of multidrug resistance of leukemia. RNAi may be a new research tool of molecular diagnosis and molecular therapy on leukemia in the future.