〔Abstract〕 Objective To analyze the magnetic resonance imaging (MRI) features and clinical manifestations of nonepithelial ovarian tumors, and to improve the preoperative diagnosis level of non-epithelial ovarian tumors. MethodsThe MRI images and clinical data of 40 patients with non-epithelial ovarian tumors confirmed by surgery and pathology were retrospectively analyzed.Results All 15 cases of mature teratoma were cystic, and the remaining 25 cases were cystic or solid, including 4 cases of immature teratoma, 8 cases of theca fibroma, 3 cases of fibroma, 5 cases of yolk sac tumor, 1 case of steroidocytoma, 3 cases of metastatic tumor, and 1 case of lymphoma. Fatty components were found in all teratomas. The immature teratoma was significantly enhanced, and the mature teratoma was slightly enhanced. Theca fibroma and fibroma showed hypointense fibers on T2WI and mild enhancement in delayed phase. The yolk sac tumor showed "honeycomb-like" changes, obvious continuous enhancement, and tortuous blood vessels. Tumor with solid component and pelvic effusion were highly correlated with malignancy (r = 0.599, P = 0.002; r = 0.553, P = 0.004), while the maximum diameter and limited diffusion of the lesions were not correlated with benign and malignant tumors (r = 0.145, P = 0.488; r = 0.230, P = 0.268). According to MRI image features and pathological results, the diagnostic rates of MRI for teratoma, theca fibroma and fibroma were 84.21 % (13/15), 100.00 % (8/8) and 100.00 % (3/3), respectively. The diagnostic rate of MRI combined with alpha-fetoprotein (AFP) for yolk sac tumor was 100.00 %. ConclusionNon-epithelial ovarian tumors have certain characteristic changes on MRI, and combine with tumor markers can improve the preoperative diagnosis rate.