Objective To explore the expressions and clinical values of serum microRNA-139-5p (miR-139-5p) in diagnosis and prognosis of patients with ovarian cancer.Methods From March 2009 to December 2011,a total of 34 patients with serous ovarian cancer and 34 female health examiners were collected in our hospital.The expressions of serum miR-139-5p before and after operation were detected in 34 patients with ovarian cancer and 34 healthy women by real-time quantitative polymerase chain reaction (RT-qPCR).The data was analyzed by t-test.The clinical values of serum miR-139-5p in diagnosis and prognosis of patients with ovarian cancer were analyzed.Results The expression of serum miR-139-5p in patients with ovarian cancer (9.45 ± 0.40) was significantly higher than that in healthy controls (3.56 ± 0.10),with a significant difference (t =14.340,P ＜ 0.001).The expression of miR-139-5p at 1 month after operation of patients with ovarian cancer (5.53 ± 0.49) was lower than that before operation,with a significant difference (t =7.800,P ＜0.001).The expression of serum miR-139-5p was correlated with lymph node metastasis (P =0.038),but was not correlated with age (P =0.728),clinical stage (P =0.118),tumor size (P =0.732) and differentiation (P =0.071).Kaplan-Meier survival curve revealed that the median survival time of ovarian cancer patients with low serum miR-139-5p expression (44.9 months) was longer than that of patients with high serum miR-139-5p expression (25.9 months),with a significant difference (x2 =5.721,P =0.017).Conclusion The expression of miR-139-5p is increased significantly in the serum of patients with ovarian cancer,which can be used as a potential biomarker for diagnosis and prognosis of patients with ovarian cancer.