Retroperitoneal hemangiopericytoma is a kind of uncommon tumor. We report a case of 41-year-old man who was diagnosed retroperitoneal tumor without significant symptoms by abdominal ultrasonography. Abdominal CT and MRI scans show a 6 cm × 5 cm solid tumor delineated clearly from adjacent organs. Excision of the tumor was performed and the histopathological examination confirmed the diagnosis of hemangiopericytoma.