Abstract: Objective To study the roles of the increased intracellular calcium induced rapidly by estrogen in the implantation of mouse blastocysts. Methods The mouse blastocysts were collected from the female mice on the pregnant day 4, divided into 3 groups: control, E2-BSA and BAPTA+E2-BSA. Immunofluorescence staining, confocal microscopy, embryo and endometrial epithenial cells co-culture and embryo transfer were used to investigate the effect of increased intracellular calcium induced by E2-BSA on the expression and localization of integrins in blastocysts and their adhesion to endometrial epithenial calls (EECs) and implantation into the endometrium. Results The increase of intracellular calcium induced rapidly by estrogen could cause the cluster and relocation of integrin αv and β3, and BAPTA might block this effect, the adhesion rate of blastocysts in contol group was 35.5%, BAPTA+E2-BSA group was 26.7% and significantly lower than 65.6% of E2-BSA group (\P\P<0.05). Conclusion The rapid increase of intracellular calcium induced by estrogen may cause the relocalization of integrin in blastocysts and their adhesion to ECCs, which is important in the process of implantation.