Objective：To investigate the expression rules of Dicer in the endometrium of early pregnant mouse and to clarify its role in embryo implantation. Methods：Real-time fluorescence quantitative PCR，immunohistochemistry and Western blot were used to detect the expressions of Dicer mRNA and protein in the mouse endometrium from unpregnant，pseudopregnant and pregnant mouse from d1 to d7. Results：During the implantation window and after the implantation（d4-d7），expression of Dicer mRNA and protein was signif－icantly higher than that before implantation and expression of d5 was the highest（PmRNA=0.000，Pprotein=0.000）. Moreover，Dicer was demonstrated in endometrial stromal cells. Conclusions：There are differences in the time and location of the expression of Dicer in endometrium of early pregnant mouse. Expression rule of Dicer in endometrial stromal cell by regulating cell growth，proliferation and differentiation may be one of the implantation mechanisms.