[Abstract] Objective To establish the rat model of ovarian Endometriosis (EMS) by using horn reversion method, and to evaluate the feasibility of establishing the rat model of ovarian EMS by horn reversion method, so as to provide an ideal animal model for exploring the pathogenesis and treatment of EMS. Methods Fifty SPF-grade female SD rats were randomly divided into five groups, namely, the sham-operated group, the 1st-week group, the 2nd-week group, the 3rd-week group, and the 4th-week group, with 10 rats in each group. An ovarian-type EMS model was established by the uterine horn refracture method, except for the sham-operated group, and the modeling success rate, the ectopic foci volume and the weight of the model were observed in each group at the 1st, 2nd, 3rd, and 4th weeks after the modeling, respectively, to evaluate the model preliminarily. Hematoxylin-eosin (HE) staining was used to observe the morphology of ectopic foci, and the expressions of proliferating cell nuclear antigen (PCNA), proliferating cell nuclear antigen (Ki67), epithelial cadherin (E-Cadherin) and neural cadherin (N-Cadherin) in uterus and ectopic foci tissues were detected by immunohistochemistry. The model was further evaluated and the degree of cell proliferation and epithelial mesenchymal transformation in different time periods after modeling was analyzed. Results The success rates of the first, second, third and fourth weeks after modeling were 80%, 90%, 100% and 100% (P>0.05).The volume and weight of ectopic foci increased significantly at 3 and 4 weeks compared with 1 and 2 weeks after modeling (P<0.01).HE staining showed endometrial epithelial cells, mesenchymal cells and a few glands in the ectopic foci. Immunohistochemical staining results showed that the expression levels of Ki67, PCNA, and N-Cadherin were significantly higher (P<0.05, P<0.01) in rat uterine tissues at 1, 2, 3, and 4 weeks after modeling compared with the sham-operated group; the expression level of E-Cadherin was significantly lower (P<0.05, P<0.01). Compared with 1 week after modeling, the expression levels of Ki67, PCNA, and N-Cadherin were significantly higher (P<0.05, P<0.01) in the uterus and ectopic foci tissues of rats at 2, 3, and 4 weeks after modeling; the expression level of E-Cadherin was significantly lower(P<0.05, P<0.01) .Conclusion The ovarian EMS model of rats can be established by uterine horn reversion method. Ectopic lesions can be observed at 1 week after operation. The success rate of modeling increases with the extension of modeling time. PCNA, Ki67 and N-Cadherin were significantly expressed in uterus and ectopic foci, and the expression levels increased with the extension of modeling time. The expression of E-Cadherin in uterus and ectopic foci decreased with the extension of modeling time. The results showed that the model formation rate of EMS rat model was high, and it could be used as a stable EMS modeling method. 【 Key words 】 endometriosis; Rat; Animal model; Reentry method