Objective To explore the effect of Huoxue Xiaoyi Formula on ovarian function and pregnancy outcome in endometriosis rats. Methods One hundred female SD rats were fed adaptively for 7 days. According to body weight, 98 rats with a normal estrous cycle were randomly divided into the blank group (n=14), the sham operation group (n=14), the donor group (n=12), and the receptor group (n=58). A rat model of endometriosis was established using allogeneic endometrial transplantation. After the model was successfully established, according to the body weight, 56 rats in the receptor group were randomly divided into the model group, and the Huoxue Xiaoyi Formula low-, medium-, and high-dose groups, with 14 rats in each group. The Huoxue Xiaoyi Formula low-, medium-, and high-dose groups were given 5.86, 11.72, and 23.44 g/kg of Huoxue Xiaoyi Formula, and the blank group, the sham operation group, and the model group were given distilled water by gavage for 15 consecutive days. According to body weight, six rats were randomly selected to take abdominal aortic blood for determination of serum anti-Mullerian hormone (AMH) content by enzyme-linked immunosorbent assay. According to body weight, six rats were randomly selected in the remaining rats to undergo high-frequency small animal ultrasound examination to measure ovarian volume and ovarian artery blood supply (resistance index and pulsatility index), and follicle count were measured. The female mice were fed with male mice at a ratio of 2:1 to observe the pregnancy rate, live fetus number, still fetus number, and absorbed fetus number. The weights of uterus and fetus were measured, while the placental weight, fetal weight, body length, and tail length were measured for live fetus. Bone and visceral malformations were also detected for live fetus. Results There were no significant differences in serum AMH and ovarian volume among the groups. Compared with the model group, the numbers of follicles in the blank group, the sham operation group, and the Huoxue Xiaoyi Formula low-, medium-, and high-dose groups were increased; compared with the Huoxue Xiaoyi Formula low-dose group, the numbers of follicles in the blank group and the Huoxue Xiaoyi Formula medium-dose group were increased (P<0.05). Compared with the model group, the resistance index and pulsatility index of ovarian artery blood flow in the blank group, the sham operation group, and the Huoxue Xiaoyi Formula low-, medium-, and high-dose groups were decreased(P<0.05). There was no significant difference in pregnancy rate among the groups. Compared with the model group and the Huoxue Xiaoyi Formula low-dose group, the live fetus number and the weight of uterus and fetus in the blank group, the sham operation group, and the Huoxue Xiaoyi Formula medium- and high-dose groups were increased (P<0.05). There were no significant differences in the still fetus number, absorbed fetus number, placental weight, fetal weight, body length and tail length among the groups. No visceral or skeletal malformations were found in the live fetal rats among the groups.Conclusion In endometriosis model rats, the ovarian artery blood flow perfusion is insufficient, and the follicle count is reduced, affecting ovary function, thereby reducing the live fetus number. After applying the Huoxue Xiaoyi Formula, it can improve ovarian blood supply, increase the follicle count, and increase the live fetus number. The effect of increasing the live fetus number with the medium- and high-doses of Huoxue Xiaoyi Formula is more significant, and there is no reproductive toxicity.