Abstract: Objective : To investigate the clinical pathological characters, therapy and prognosis ofthe low-grade malignant endometrial stromal sarcoma (ESS). Methods : Among the 11 cases of the low-grade malignant endometrial stromal sarcoma, 9 cases were excised uterus,double sides accessoriesand pelvic cavity lymph node, 2 cases were excised uterus and one side accessory. During 2-8 years'sfollow-up, 11 patients were still well. Results : Pathological characters: Uterus increases equably. Mosttumors are located at the fundus of uterus's posterior wall. The sectioned surface of the tumors ishoariness or lark,and its texture is crisp,and sometimes the tiny bursal cavities are seen. On themicroscopic examination:The tumor cells look like the endometrial stromal cell of proliferation phase,and the helical veins are often found. The tumor cells present ligulate-invasion reaching the muscularlayer or many infiltrating foci,But there is no transmigration with the surrounding smooth musclebundles. The tumor tissue is lack of gland component. One case of the 11 cases is companied withepithelioid sexual cord differentiation,and one case is companied with smooth muscle differentiation.Immunohistochemistry: The knubbly cells have expression to Vimentin,SMA,Desmin,KP-1,ER,PR. Conclusions : The low-legree malignant ESS has a diversity of pathological characters. Theimmunohistochemistry redounds to diagnosis and differential diagnosis. The pre-operation diagnosticcurettages and mid-peration frozen section can improve the rate of diagnosis. Excising the wholeuterus and double side accessories can reduce the relapse. The prognosis of this disease is better.