Objective：To investigate the effects of checkpoint kinase 1 siRNA transfection on the proliferation and cell cycle of human ovarian carcinoma HO8910 cells and its mechanisms. Methods：Three Chk1 siRNA targeting fragments were designed and synthe－sized. After the transfection，Western blot was conducted to determine the expression of Chk1 at protein level. The effective Chk1 siR－NA fragment was transfected into HO8910 cells，and MTT method and flow cytometry analysis were used for determining the influence of Chk1 siRNA on the proliferation and cell cycle，respectively. Then，Western blot was used to detect cell cycle of related genes Cy－clinA，CDK4 and Cdc25A at protein level. Results：One fragment among 3 Chk1 siRNAs was valid. In HO8910 cells，after transfec－tion with the effective Chk1 siRNA，the protein level of Chk1 was decreased about 75.3%，significantly lower than that in the non-transfected group and liposome transfection group（P=0.000）. At 48 h after transfection，the activity of cell proliferation was inhibited with an inhibition rate of （52.1±5.1）%，significantly higher than that in the liposome transfection group（7.6±3.8）%（P=0.000）. Flow cytometry showed that the proportion of HO8910 cells in G2/M phase was （5.03±2.62）%，significantly lower than that in the non-transfected group（19.35±2.19）% and liposome transfection group（19.76±2.67）%（P=0.000）. Western blot results showed that in the HO8910 cells transfected with Chk1 siRNA，the protein levels of CyclinA，CDK4 and Cdc25A were enhanced，which were statis－tically different compared with those of non-transfection group and liposome group（P=0.000）. Conclusion：After Chk1 gene silencing by siRNA，the proliferation of the human ovarian carcinoma HO8910 cells was inhibited，which was related with the block－ade of G2/M phase arrest.