Abstract: Objective To study the diagnostic and treatment methods of malignant ovarian tumor in pregnant women. Methods Diagnosis,treatment and prognosis of ovarian malignant tumor in 3 pregnant women were retrospectively analyzed with the related literature reviewed. Results Among the 3 869 pregnant women admitted to our hospital in the past two years for childbirth,early ovarian cysts were found in 2 and a giant pelvic tumor in 1 by ultrasonography.The tumor was removed in caesarean section.Pathology examination showed that the tumor was a highly differentiated ovarian epithelial cancer,which was removed by cytoreductive surgery and received chemotherapy.The patient had a tumor-free life when we wrote this paper.Two were suspected with malignant ovarian tumor before operation,one of them underwent exploratory laparotomy,chemotherapy,removal of mediastina metastatic tumor 27 weeks after gestation with a reversion tendency.The patient had a tumor-free life when we wrote this paper.The other received caesarean section and exploratory laparotomy at the 32⁺² gestational weeks.She was diagnosed as metastatic ovarian tumor from stomach and died of general metastasis after 6 months.The 3 newborns were healthy when we wrote this paper. Conclusion Malignant ovary tumor in pregnant women should be treated according to its histology type and phase,and the gestational weeks and will of pregnant women.