Abstract： Objective To investigate the relationship between expression of eofilin-1 and in vivo implantation capacity of eutopic endometrium of endometriosis.Methods Eutopic endometrium of 20 cases with stage Ⅲ or Ⅳ endometriosis were obtained by laparoscopic or laparotomy surgery (endometriosis group) matched with 20 cases of eutopic endometrium from patients with cervical cancer in situ (control group) in Department of Obstetrics and Gynecology,ShengJing Hospital.All cases' eutopic endometrium were collected and injected into abdominal cavity of nude mice to establish endometriosis animal model, then the successful rate of animal model and volume of endometriosis lesion were calculated.The expression and positive rate of eofilin-1 protein were measured by western blot and immunohistochemistry staining.Results The mean volume of endometriosis lesions (2.38 ± 0.22)mm~3 in endometriosis group was significantly bigger than (0.36 ± 0.08) mm~3 in control group (P < 0.05).The successful rate of establishing endometriosis model was 95% (19/20) in endometriosis group and 5% (1/20)in control group, which reached statistical difference(P <0.05).The expression and positive rate of cofilin-1 protein in eutopic endometrium and the expression of cofilin-1 protein in endometriosis lesion of animal model were 0.82±0.06, 90% (18/20), 0.85 ± 0.03 and 0.21 ± 0.03, 20% (4/20), 0.22 ± 0.02 in control group, which reached statistical difference(P <0.05).The successful rate of establishing endometriosis model with positive cofilin-1 in endometrium 86% (19/22) was significantly higher than 6% (1/16) of model's endometrium with negative cofilin-1 expression(P <0.05).Conclusions Implanting capacity and cofilin-1 expression level of eutopic endometrium of endometriosis were more intensive than that of normal endometrium.High cofilin-1 expression was probably related with implanting capacity of eutopic endometrium of endometriosis.