Abstract: Objective　To investigate the differential diagnosis significance of high and low grade serous ovarian cancer with carbohydrate antigen 125（CA125）. Methods　A total of 128 patients with ovarian tumors were retrospectively analyzed. The serum levels of CA125 of patients with high and low grade serous ovarian cancer and cystadenocarcinoma were determined preoperatively. Results　Serum levels of CA125 among the high and low grade serous ovarian cancer patients were significantly higher than those of serous cystadenocarcinoma patients，respectively（P＝0.002，P＝0.003）. The serum levels of CA125 between the high and low grade serous ovarian cancer patients showed no statistical significance（P＝0.426）. Conclusions　Serum CA125 plays an important role in the differential diagnosis of malignant ovarian tumors，but it cannot identify the high and low grade serous ovarian cancer.

Key words: Carbohydrate Antigen 125, ovarian cancer, high grade, low grade