Objective MRI diagnosis and pathological analysis of borderline ovarian mucinous cystadenocarcinoma. Methods A retrospective analysis of clinical data and MRI image data was carried out in 35 patients with borderline ovarian mucinous cystadenocarcinoma confirmed by pathology in our hospital, tumor location, shape, size, the number of housing, cystic fluid signal, nodules or papillary projections, cystic wall and partition thickness were observed, results were cross-check analyzed with pathology. Results Pathological comparison showed that MRI found out all tumors (37 tumors), tumor detection rate were 100%, main tumors were complete cystic and cystic tumors. In 35 cases, 16 cases were on the left, 17 cases were on the right, 2 cases were bilateral; 30 tumors were oval tumors, 7 tumors were lobulated. There was no significant difference in tumor size diagnosis in MRI and pathological results (P>0.05). Conclusion MRI can diagnose borderline ovarian mucinous cystadenocarcinoma better, display that the tumor location, size and shape, pathological feature, cellular ovary, T2WI low signal cyst fluid, T1WI with high signal cyst fluid, nodules or papillary projections (≥5mm) and cystic wall or irregular thickened septum (≥5mm) 5 MRI siigns have important value in its differential diagnosis, can provide imaging bases for clinical treatment.