Abstract: Objective To explore the expression level of membrane-associated protein Numb in epithelial ovarian carcinoma and its relationship with ovarian cancer stem cell markers CD117, CD133, acetaldehyde dehydrogenase 1(ALDH1). Methods A total of 136 patients who had ovarian tumors and 22 patients who had not ovarian tumors in Department of Gynaecology and Obstetrics, West China Second University Hospital, Sichuan University were chosen as the study subjects. According to the histopathologic examination results, they were divided into epithelial ovarian carcinoma group (n=92), ovarian borderline tumor group (n=23), ovarian benign tumor group (n=21) and normal ovary group (n=22). Expression levels of Numb protein, CD117, CD133 and ALDH1 in ovarian tissue were detected by immunohistochemical SP method and these several kinds of protein expression differences and correlation statistical analysis were performend. Results ① The positive expression rate of Numb protein in epithelial ovarian carcinoma group was higher than that in benign tumor or normal ovary group, also Numb protein positive expression rate in ovarian borderline tumor group was higher than that in normal ovary group, and the differences were statistically significant (P<0.05). ② Numb protein positive expression rate in ovarian tissue in patients with epithelial ovarian carcinoma FIGO stageⅠ-Ⅱ was lower than that in stage Ⅲ-Ⅳ, also the same in no lymph nodes metastasis compared with lymph nodes invasion, and the differences of positive expression rate were statistically significant (P<0.05). While there were no significant differences among different age, histopathological types, pathological grades and residual tumor size (P>0.05). ③ There was no correlation between Numb protein and CD117 and CD133 positive expression rate in epithelial ovarian carcinoma tissue 〔correlation coefficient (r)=0.116, P=0.261; r=0.083, P=0.425〕. However, the positive expression rate of Numb protein and ALDH1 was positively correlated (r=0.296, P=0.261). Conclusion The expression of Numb protein may involve in the occurrence, invasion and mechanisms of ovarian cancer, positively correlated with ovarian cancer stem cell markers ALDH1, and may affect the prognosis of patients.