Malignant melanoma is a kind of highly malignant tumor from melanocytes, referred to as malignant black, accounting for 1% to 3% of systemic malignant tumors. The tumor can occur in many organs and tissues throughout the body, but mostly occurs in the skin, oral, esophageal, anal, vaginal mucosa, oculocutaneous, and meningeal membranes can also occur. Those occurring in the gastrointestinal tract are mostly metastatic, and primary is less common. There are two pathological types of gastrointestinal malignant melanoma: polypoid nodular type and infiltrative ulcerative type. Polypoid lesions are more common and larger, have diversity, are non-melanotic, and often cause symptoms of intestinal obstruction. Infiltrative ulcerative lesions are often solitary and have hyperpigmentation. The histologic changes of gastrointestinal melanoma are similar to those of cutaneous origin and are histologically diverse. The more common histology is a glandular vesicular arrangement of small vesicles or solid nests of epithelioid tumor cells and nevus-like cells, which may be diffusely or lamellarly distributed in areas of active growth. Those occurring in the gastrointestinal tract are easily confused with poorly differentiated adenocarcinoma and need to be differentiated. At present, positive immunohistochemical staining for specific marker antibodies of melanocytes is the main diagnostic and differential diagnosis, of which HMB45 is 100% specific and 93% sensitive for malignant melanoma, which detects specific proteins of melanosomes and positive signals in the cytoplasm; Vimentin (wave protein) is specific to melanocytes and melanoma cells, and is of great value in differentiating anaplastic melanoma from epithelial or neurogenic tumors for the diagnosis of melanoma; S100 is more sensitive and less specific. The histological characteristics and immunophenotype of the tumor support the diagnosis of malignant melanoma, and no definite tumor was found in other parts of the body, which should be the primary lesion. The prognosis of malignant melanoma of the gastrointestinal tract is poor. In recent years, some progress has been made in the treatment of melanoma at home and abroad, but the overall efficacy is still unsatisfactory, and there is still time for us to further explore the research.