Clinically, it is thought that the greenish tongue may be caused by the administration of quinoform, which is used to treat subacute spinal optic neuropathy, and is not an early stage of any disease. Through the observation of tongue coating bacterial culture and bacterial quantification, tongue temperature, acidity and alkalinity, fluorescence phenomenon, microscopic examination of tongue coating and pathological biopsy, it is found that the color of tongue coating is related to the color of the dominant colonies, and may also be related to smoking, drugs, food, saliva and so on. So green tongue coating does not mean that there is any major disease in the whole body. If the tongue is green, you can brush your teeth and rinse your mouth in time, and it is possible that the green color of the tongue is removed through the mechanical friction effect of brushing, eating, and talking, or you can go to the stomatology department of the regular hospital for examination to find out what causes the green color of the tongue.