Abstract: Objective To investigate the apoptosis induced by FMS-like tyrosine kinase 3 (FLT3)- targeted inhibition in acute myelocytic leukemia cell lines THP-1,HL-60,for to explore the efficacy of abnormal over-expression of FLT3 on AML patients. Methods After downregulating FLT3 expression by FLT3-small hairpain interfering RNA (FLT3-shRNA) in THP-1,HL-60 cells,Annexin V-FITC method were used to adjusted the early apoptosis,the special DNA ladder and TUNEL staining in situ cytohybridization were used to detect the later apoptosis,the distribution of cell cycle was assayed by FCM. Results Compared with controls,the early apoptosis rate both in THP-1 and HL-60 cells transfected with FLT3-shRNA detected by Annexin V-FITC were statistically increased（P＜0.01）,DNA Ladder which is characteristic of apoptotic cell was seen,and cells showed an increase in the percentage of cells in the phase G0/G1 (P＜0.01) and a decrease in the percentage of cells in the phase S (P＜0.05).Otherwise,and the result of TUNEL in THP-1 cells also showed an increase of apoptotic cells (P＜0.01). Conclusion shRNAi-mediated FLT3 suppression can induces cell apoptosis in both THP-1,HL-60 cells,thus tentatively confirms the effects of FLT3 over-expression on anti-apoptosis in AML.