To investigate the protective effect of Fuzi Lizhong Pills on endometriosis(EMT) rats and the intervention effect on the programmed cell death protein 1(PD-1)/programmed death ligand-1(PD-L1) signaling pathway.Methods:The EMT model was induced in SD rats in the estrous cycle by autologous endometrial transplantation，and the model rats were randomly divided into a model group，an experimental group，and a control group，with 15 rats in each group.The rats in the experimental group and the control group were treated with Fuzi Lizhong Pills at 20 g/kg and danazol suspension at 0.1 g/kg by gavage，respectively，while those in the model group were treated with the same amount of normal saline，once per day.After continuous intervention for three weeks，the ectopic endometrial volumes of rats before and after drug intervention were observed.The expression of vascular endothelial growth factor(VEGF) in the ectopic endometrial tissues of rats was detected by immunohistochemistry，and the expression of PD-1 and PD-L1 proteins in the in situ and ectopic endometrial tissues of rats was detected by Western blot.Results:The volumes of ectopic endometrium in the model，experimental，and control groups after intervention were(139.85±12.43)，(64.52±6.78)，and(76.48±6.27) mm3，respectively.Immunohistochemical analysis showed that the relative expression of VEGF protein in ectopic endometrial tissues was(35.57±5.53)%，(13.41±2.43)%，and(16.59±3.05)%，and the immunohistochemical scores were(3.89±0.52)，(1.88±0.13)，and(2.69±0.24) points，respectively.Western blot showed that the relative expression of PD-1 in the in situ endothelial tissues of the model，experimental and control rats was 1.65±0.24，0.32±0.04，and 0.68±0.14，respectively，and the relative expression of PD-L1 protein was 1.16±0.14，0.42±0.15，and 0.63±0.08，respectively.Additionally，PD-1 relative expression in ectopic endothelial tissues was 0.89±0.04，0.45±0.06，and 0.63±0.08，respectively，and PD-L1 protein relative expression was 0.78±0.06，0.28±0.03，and 0.41±0.06，with a statistically significant difference(P<0.05).Conclusion:Fuzi Lizhong Pills can inhibit VEGF expression，promote endometrial atrophy in ectopic endometrium of EMT rats，and inhibit the activation of the PD-1/PD-L1 signaling pathway.