[Objectives] In order to study the effects of different doses of pregnant mare serum gonadotropin (PMSG) on ovarian morphology and early embryo development in vitro after superovulation in rabbits (Oryctolagus cuniculus f. domesticus). [Methods] Twenty-four rabbits were randomly divided into four groups, with 6 rabbits in each group. The control group was not treated. The latter three groups were injected with 50 IU, 70 IU and 90 IU PMSG , and 100 IU human chorionic gonadotropin (HCG) for superovulation. After dissection, the morphology and tissue parameters of ovaries were measured. Embryos were flushed from the left and right Fallopian tubes into Petri dishes by using 5 ml washing solution and then transferred to the cell culture room for in vitro culture and observation. The results were expressed as “Mean ± standard deviation, and the data were analyzed by one-way ANOVA with SPSS 25.0. P < 0.01 means the difference is extremely significant, P < 0.05 means the difference is significant, and P ≥ 0.05 means the difference is not significant. [Results] The results showed that compared with the control group, the weight, width, and thickness of ovaries in the PMSG-treated group increased extremely significantly (P < 0.01), the length of ovaries increased significantly (P < 0.05), the surface of ovaries became congested, and the number of follicles increased with the increase of PMSG injection dose (Fig. 1, Table 1). In addition, with the increase of PMSG injection dose, the diameters of secondary follicles and their enclosed oocytes, and the diameter of tertiary follicles decreased (P < 0.01), while the diameter of oocytes in tertiary follicles increased, with a significant difference compared with the control group (P < 0.05, Fig. 3, Table 3). The diameter of tertiary follicles and the dominance rate of follicles in the 70 IU group were significantly higher than those in the control group, 50 IU group, and 90 IU group (P < 0.05, Table 4). When the embryos were cultured in vitro, compared with the control group, PMSG treated group had a significantly higher embryo deformity rate (P < 0.01), significantly lower 2-cell rate (P < 0.01), and significantly lower 4-cell rate (P < 0.05, Fig. 2, Table 2) due to the increase of PMSG injection dose. [Conclusion] 90 IU PMSG superovulation can cause adverse effects, while 70 IU PMSG can increase the numbers of follicles at all levels and the dominance rate, and promote the development of oocytes in tertiary follicles, but reduce the diameters of follicles at all levels.