Abstract: This experiment was conducted to study the effect of intraperitoneal injection of N-methyl-D-aspartic acid (NMDA) on estrus rate and number of early embryos and fetuses in female mice. A total of 40 Kunming mice weighing (26±1.37)g were selected and randomly allocated into the following two groups: a control group (n=20) received intraperitoneal injection of 0.2 mL normal saline, and an experimental group (n=20) received intraperitoneal injection of 0.2 mL NMDA solution. The vaginal mucus was sampled by dipping with a cotton swab. The smeared samples were stained with HE staining method to determine the estrus of the mice. On the 3rd day after the mating of estrus female mice and male mice, 10 mice were randomly selected from each group and sacrificed by cervical dislocation. After embryos flush, the number of embryos was observed under the stereomicroscope. On the 9th day after the mating, the remaining mice were sacrificed and their uteri were collected to count the number of fetuses. The results showed that compared to the control group, the estrus rate, embryo number and fetuses number of the mice in NMDA group were increased by 28.57%, 18.18% and 12.94%, respectively. In conclusion, intraperitoneal injection of NMDA can promote the estrus of female mice and increase the number of early embryos and fetuses, which provides a theoretical basis for the application of NMDA in animal reproduction.