The black color of the inner wall of the mouth may be caused by hyperpigmentation, trauma, and black spot polyp syndrome. 1. Hyperpigmentation: If you usually smoke or drink coffee frequently, it may lead to brown or black pigmentation on the inner wall of the mouth, thus making the inner wall of the mouth appear black. 2. Trauma: If there are burns or bites in the mouth, the blood vessels of the oral mucosa may rupture and bleed, and local bruising may occur, so the patient will have black petechiae on the inner wall of the mouth. 3. Black spot polyp syndrome: black spot polyp syndrome may be caused by autosomal dominant inheritance, patients with lips, buccal mucosa, palms, soles, face and other parts of the pigmentation, the majority of patients often appear oral, lip mucosa black spot. It is recommended that patients with black oral cavity lining need to consult a doctor in a timely manner, and the doctor will choose the appropriate measures for treatment according to the patient’s disease.