Objective: To investigate the potential effect of pure total flavonoids from Citrus paradisi Macfad peel(PTFC) on the proliferation and apoptosis of human myeloid leukemia cells Kasumi-1, HL-60 and K562, and the underlying mechanisms. Methods: PTFC was extracted from Citrus paradisi Macfad peel and was identified by high performance liquid chromatography. The effect of PTFC on the proliferation and apoptosis of leukemia cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, fluorescent microscopy and flow cytometry, respectively. The effect of PTFC on the expression levels of apoptosis-related regulators was determined by Western blot assay. Results: Treatment with PTFC inhibited leukemia cell proliferation in a dose-and time-dependent manner and triggered Kasumi-1 cell apoptosis. Treatment with PTFC significantly increased the levels of activated poly adenosine diphosphate-ribosepolymerase and caspase-3/-9, but reduced the levels of Mcl-1 expression in Kasumi-1 cells. However, PTFC did not obviously induce HL-60 cell apoptosis. Conclusion: PTFC inhibited leukemia cell proliferation and induced their apoptosis by modulating apoptosisrelated regulator expression in leukemia cells in vitro. Objective: To investigate the potential effect of pure total flavonoids from Citrus paradisi Macfad peel (PTFC) on the proliferation and apoptosis of human myeloid leukemia cells Kasumi-1, HL-60 and K562, and the underlying mechanisms. Methods: PTFC was extracted from Citrus paradisi Macfad peel and was identified by high performance liquid chromatography. The effect of PTFC on the proliferation and apoptosis of leukemia cells were determined by 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide, fluorescent Results of Treatment with PTFC inhibited leukemia cell proliferation in a dose-and time-dependent manner and triggered Kasumi-1 cell apoptosis. Treatment with PTFC significantly increased the levels of activated poly adenosine diphosphate-ribose polymerase and caspase-3 / -9, but reduced the levels of Mcl-1 expression in However, PTFC did not obviously induce HL-60 cell apoptosis. Conclusion: PTFC inhibited leukemia cell proliferation and induced their apoptosis by modulating apoptosisrelated regulator expression in leukemia cells in vitro.