Objective. To detect the expression levels of microRNA-200a/b (miR-200a/b) in tumor tissues and serum of patients with epithelial ovarian cancer (EOC) and to explore its clinical significance. Methods. A retrospective selection of 30 cases of benign ovarian disease or healthy physical examination (control group) and 55 cases of EOC patients. Real-time quantitative PCR was used to detect the expression level of miR-200a/b in tumor tissues and serum, and the miR-200a/b expresses relevance in the two types of samples were evaluated at the same time. Receiver operating characteristic curve (ROC) and Kaplan-Meier survival analysis were used to evaluate the diagnostic value of miR-200a/b expression and its influence on prognosis, respectively. Results. The serum and tissue miR-200a/b expression levels in EOC patients were higher than those in the control group (