Objective: To explore the effects of vinyl chloride monomer (VCM) on cell cycle and apoptosis of hepatocytes in rats.Methods: Sixty-four Sprague Dawley (SD) rats (half male and half female) were randomly divided into negative control group (25mg/kg clean air) and three experimental groups exposed to 5, 25, and 125mg/kg VCM.The rats were treated with clean air and different doses VCM by intraperitoneal injection with three times a week for twelve weeks, and rats were killed at the 6th and 12th week.Flow cytometry (FCM) was applied to detect cell cycle and apoptosis rate in hepatocytes.Results: Exposed for 6 weeks,the percentage of G0/G1 phase in 5, 25mg/kg VCM experimental groups were (69.73±10.94) and (74.32±9.29) which were higher than the control group (56.13±10.65) (P<0.05), the percentage of S phase in 25mg/kg VCM experimental group (1.80±2.11) was statistically significant difference from the control group (12.82±5.85), (P<0.01).But the percentage of G0/G1 phase did not showed significant difference compared to control group (P>0.05)while the percentage of S phase in 125mg/kg VCM experimental group (14.91±4.43) was statistically significant difference from the control group (6.68±2.64), (P<0.01) when exposed to VCM for 12 weeks.The apoptosis rates of liver cells in rats did not change significantly.Conclusion: VCM may induce G0/G1 phase and S phase arrest of hepatocytes in rats.VCM affect the function of G1/S phase checkpoint.