The study was purposed to investigate the apoptosis of HL-60 cells induced by recombinant common buckwheat trypsin inhibitor (rBTI) and its mechanism. The inhibition rate of rBTI on HL-60 cells was detected by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide); the morphology of HL-60 nuclei was observed by fluorescence microscopy; the apoptosis cells of HL-60 detected by agarose gel electrophoresis and the changes of apoptosis rate was assayed by flow cytometry (FCM), when the HL-60 cells were treated with different concentration of rBTI for 24 hours. The results showed that the growth of HL-60 cells was inhibited evidently after treatment with rBTI in a dose-dependent manner, but there were minimal effects on normal human peripheral blood mononuclear cells (PBMNCs). The nuclei of HL-60 cells showed the characteristics of apoptosis, the analysis by flow cytometry indicated that the apoptosis rate of HL-60 cells was 52% after treatment with rBTI (100 microg/ml), DNA analyzed by agarose gel electrophoresis showed "ladder" pattern. It is concluded that rBTI obviously inhibits growth of HL-60 and induces its apoptosis which provides a foundation for use of recombinant common buckwheat trypsin inhibitor to cure the acute myeloid leukemia.