Abstract: Objective To investigate the effect of S-Trityl-L-Cysteine on the mitosis arrest and apoptosis of acute leukemia HL-60 cell,and approach the causality of mitosis arrest and apoptosis in HL-60 cell under the drug treatment. Methods HL-60 cell was exposed to various concentrations of STLC (1,2.5,5,10,50,100 μmol/L) and compared with the control group.The inhibitory effects was detected by MTT assay, and Trypan blue staining assay was used to examine the number of cell activity. Cell cycle arrest and sub-G₁ was detected by flow cytometry assay and character of cell and its nuclear were observed by immunofluorescence staining, Annexin-v/PI assay was used to annlyse the apoptosis rates of normal bone marrow cells treated by STLC. Results MTT and Trypn blue staining assay revealed that STLC inhibited HL-60 cell growth and induced its death.The typical phenomenon of mitotic catastrophe was observed by immunofluorescence staining.STLC induced apoptosis on HL-60 in dose and time dependent and with the augment of STLC, the rate of G₂/M arrest increased in 24h and 48h, but no significant change in 72h.Further study revealed G₂/M arrest and apoptosis were cencurrent in early stage of drug treament. The mitotic arrest was reversibly after the drug removed. The apoptosis rates of normal bone marrow cells was slightly increase under the drug treatment. Conclusion S-Trityl-L-Cysteine induces G₂/M arrest and apoptosis in HL-60 cell and manifest more potential effects on antimitotsis and antitumour. Simultaneous of G₂/M arrest and apoptosis suggests that there is an possible new mechanism in the early stage of drug treatment.