The black spot with regular shape on one side of the mouth may be caused by occlusal trauma, which needs no special treatment. If it is caused by mercury poisoning, black spot polyp syndrome, etc., it needs to take general measures, medication and surgical treatment for the cause of the disease. 1. Occlusal trauma: if the recent process of chewing food, inadvertently bite the oral mucosa after the emergence of blood bubbles, when it becomes bruises will form a more regular similar to the black spot, generally do not need special treatment, after a period of time can be healed on their own. 2. Mercury poisoning: some patients’ oral mucosa will appear blue-black mercury lines, which can be manifested as a black spot on one side of the mouth grows regular. Patients need to cooperate with the doctor to wash the stomach, but also to follow the doctor’s instructions to use 50% magnesium sulfate diarrhea. Secondly, it is also necessary to follow the doctor’s instructions to apply sodium dimercaptopropanesulfonate or dimercaptopropanol and other mercury-repellent drugs, and if acute renal failure occurs, it is necessary to take hemodialysis or hemoperfusion treatment. 3. Black spot polyp syndrome: Typical symptoms are hyperpigmentation of the lips, cheek mucosa, etc., which may be manifested as regular black spots on one side of the mouth. If the polyp is smaller than 0.5cm, observation is the main focus for the time being, if the volume is greater than or equal to 0.5cm, endoscopic resection, open polypectomy is required. It is recommended that people with regular black spots on one side of the mouth should go to the hospital in time to improve the examination and cooperate with the doctor to treat the original disease.