Objective: To evaluate the clinical significance of platelet (PLT) count in epithelial ovarian cancer, and to inves-tigate the correlation between thrombocytosis and the incidence of epithelial ovarian cancer. Methods: We evaluated 220 epithelial ovarian tumor patients divided into early stage epithelial ovarian cancer group (n = 80), advanced stage epithelial ovarian cancer group (n = 50) and benign ovarian tumor group (n = 90) as controls, who underwent primary surgical treatment. Three groups were evaluated with the relationship between platelet counts and preoperative and postoperative CA125, histo-pathology, abdominal edema, residual tumor, and lymph node metastasis. Epithelial ovarian cancer patients were evaluated whether platelet count was decreased after surgery. Results: The mean platelet counts were (234.55±71.51)×109/L in the early stage epithelial ovarian cancer group, (308.12±111.95)×10/L in the advanced stage epithelial ovarian cancer group,and (206.28±52.62)×109/L in the benign ovarian tumor group, with a significant difference among the 3 groups (P<0.05).In the early stage epithelial ovarian cancer group, the platelet count was correlated with histopathology. In the advanced stage epithelial ovarian cancer group, there was a correlation between thrombocytosis and the incidence of that residual tumor diameter was greater than 2 cm. But there was no relationship between platelet count and histopathology, CA125, abdominal edema, or lymph node metastasis. In general the platelet count was decreased after surgery. Conclusion: An increased platelet count is commonly seen in patients with epithelial ovarian cancer, but it usually decreases after surgery. Patients with thrombocytosis have poor prognosis. Platelet count can be used as a marker for the development and prognosis of epithelial ovarian cancer.