Leptomeningeal melanomatosis is a rare nervous system neoplasm, which may perform varieties of clinical symptoms, as well as it is difficult to make the right diagnosis.We describe here a rare case of a primary leptomeninge melanomatosis.A 24 years old man was admitted after headache repeatedly for a month with increased intracranial pressure (ICP).Cerebral imaging suggested thickening of leptomeninge, with obvious enhancements on MR enhancement scanning.No solid mass was found.After pathological and immunohistochemical examinations of cerebrospinal fluid (CSF), we found that tumor cells with positive of S-100 protein and HBM-45, which behaviors were in accord with melanophore.By taking a thorough physical examination, no other tumor was suspected.Combining with the clinical features, physical examinations, laboratory examinations and cerebral imagings, we made a diagnosis of primary leptomeninge melanocytosis.In addition, we found a great convenient, safe and efficient way in investigation and treatment-by inserting Ommaya reservoir.This article is emphasized on the diagnosis and treatment of primary leptomeningeal melanomatosis, especially on the using of Ommaya reservoir.