Objective:To investigate the expression rule of Cyclin-E in endometrium during the early pregnancy and its role in blastocyst implantation in mice.Methods:RT-PCR and immunohistochemistry techniques were applied to detect Cyclin-E gene and protein expression in endometrium from pregnant mice on days 1～7.In addition Anti-cyclinE antibody was injected into horns of uterus of day 3 pregnant mice to observe the numbers of implanted blastocysts.Results:Expression of Cyclin-E gene and protein in pregnant mice were steady increasing since day 2 and reaching maximal level on day 5 of pregnancy.Injection of Anti-cyclinE antibody could decrease the numbers of implanted blastocyst compared with that of saline-injected group.Conclusion:Cyclin-E were persistently expressed in mouse endometrium during the early pregnancy and might be concerned with proliferation differentiation of endometrium and participates in the regulation process of mouse blastodyst implantation.