Objective: To establish a system in detecting the cell cycle specificity induced by recombinant human Fas ligand in vitro, so as to provide a reliable platform for further exploring the mechanism of cell cycle control and regulation in Fas-medi- ated apoptosis. Methods: The target cells—leukaemia cell lines and activated peripheral blood lymphocytes stimulated by phytohemagglutinin were incubated with recombinant human Fas ligand for 6 to 36 h, apoptosis was detected by sub-G1, com- mon annexin-V/PI and modified annexin V and propidium iodide (API) methods and analysed by flow cytometry. Results: The modified API method demonstrated that Fas-mediated apoptosis was cell cycle specific and initiated at G1 phase. The common annexinV/PI method showed the most appropriate condition for the detection of typical cell cycle-specific apoptosis. The sub-G1 method could only illuminate late apoptosis and DNA histogram. Conclusion: Fas-mediated apoptosis was cell cycle-specific and initiated at G1 phase. Based on the modified API and common AnnexinV/PI methods, the establishment of stable and typical cell cycle-specific model in Fas-mediated apoptosis in vitro was feasible. Objective: To establish a system in detecting the cell cycle specificity induced by recombinant human Fas ligand in vitro, so as to provide a reliable platform for further exploring the mechanism of cell cycle control and regulation in Fas-mediate apoptosis. Methods: The target cells-leukemia cell lines and activated peripheral blood lymphocytes stimulated by phytohemagglutinin were incubated with recombinant human Fas ligand for 6 to 36 h, apoptosis was detected by sub-G1, com-mon annexin-V / PI and modified annexin V and propidium iodide (API) methods and analyzed by flow cytometry. Results: The modified API method called that Fas-mediated apoptosis was cell cycle specific and initiated at G1 phase. The common annexin V / PI method showed the most suitable condition for the detection of typical cell cycle -specific apoptosis. The sub-G1 method could only illuminate late apoptosis and DNA histogram. Conclusion: Fas-mediated apoptosis was cell cycle-specific and initiated at Based on the modified API and common Annexin V / PI methods, the establishment of stable and typical cell cycle-specific model in Fas-mediated apoptosis in vitro was feasible.