The urokinase plasminogen activator system, which consists of urokinase plasminogen activator (uPA), plasminogen activator inhibitor type-1 (PAI-1) and urokinase plasminogen activator receptor (uPAR), plays an important role in tumor invasion and metastasis, and it may be a potential diagnostic biomarker and therapeutic target in cancer. It has been found that the expression of uPA and PAI-1 in ovarian cancer is related to clinical pathologies, while their effects on the biological behavior of tumor cells and their clinical significance are still unknown. In this study, 100 tissue samples (60 samples from malignant tumors, 20 from benign tumors and 20 from controls) and 147 blood samples (49 samples each from patients with malignant tumors, benign tumors and control group, respectively) were analyzed. The positive expression levels of uPA and PAI-1 in the malignant tumor samples and their serum concentrations in the malignant group were all significantly higher than these levels in the benign tumors and controls. In addition, the levels in patients with poorly differentiated and stage III-IV cancers, cancers with metastases as well as residual tumors >2 cm after surgery, were all obviously increased, consistent with their concentrations in serum. The Cox model analysis showed that expression of uPA at the transcription level had significant associations with prognosis. In addition, uPA greatly enhanced the abilities of cell invasion, migration and adhesion through its overexpression in SKOV3 cells. Collectively, our results showed that uPA and PAI-1 play important roles in ovarian cancer development; therefore, their expression in tissues and their concentrations in serum would greatly assist the diagnosis and prediction of the prognosis in ovarian cancer.