One case of histiocytic sarcoma of the spleen is reported. The patient, a 54-year-old female, presented with a huge soft tissue mass with a clear border and pseudo capsule in the splenic parenchyma on CT. The density of the mass was uneven, multifocal cystic necrosis and irregular bleeding were observed inside, but no calcification could be seen. On contrast-enhancement scan, the solid component of tumor exhibited moderate progressive enhancement, and area of cystic necrosis exhibited no enhancement. In MRI, T1WI showed mixed low signal, and T2WI showed mixed slightly high signal. The pathological diagnosis was histiocytic sarcoma.