A black mole on the tongue may be caused by heredity, or may be caused by pigmented nevus, hemangioma and other diseases. 1. Heredity: Some people may have congenital nevus on the tongue due to the difference in physical condition. If there is a nevus from birth and there is no other uncomfortable symptom accompanying the nevus, it is mostly considered to be caused by heredity, and there is no need to worry about it in general. 2. Pigmented nevus: the cause of pigmented nevus is not yet clear, it may be related to drugs, trauma, hormone level change and other factors. Patients may have brown or black pigmented nevus on the tongue. 3. Hemangioma: the etiology and pathogenesis of hemangioma are not yet clear, it may be caused by gene mutation, abnormal transformation of endothelial cells, daily exposure to fertilizers and pesticides and other factors. Patients will have plaques and papules locally, which will be manifested as a nevus on the tongue. There are many reasons for the development of nevus on the tongue, and it is recommended that patients go to a regular hospital to undergo a relevant examination to identify the cause of the disease. Once the diagnosis is confirmed, treatment measures should be taken.