Oral cancer ranks sixth among the common malignant tumors in the world. To attach importance to the prevention and treatment of oral cancer, we should first pay attention to the prevention and treatment of oral precancerous lesions. Long-term chronic stimulation, such as smoking and drinking a lot of alcohol, eating overheated food, stimulation of oral mucosa by residual teeth or unsuitable dentures, etc., can rub the buccal mucosa or lingual mucosa, causing erosion, ulceration and hyperplasia, and these damage lesions, if not healed for a long time, can easily cause cancer, which is oral precancerous lesions. How to identify oral cancer and precancerous lesions Oral ulcers: ulcers that do not heal for a long time, especially those with slightly elevated edges, should be thought of as cancer. However, it should be distinguished from “decubitus ulcer” formed by teeth rubbing on the edge of the tongue, by grinding away the steep tip of the teeth or removing the remaining teeth, and observing the ulcer healing for 2 weeks, which can be ruled out. White spots in the oral cavity: are precancerous lesions in the oral cavity, with a cancer rate of 5% to 7%. The white spots are light white in the early stage, which are mostly found occasionally when examining the oral cavity. Over time, it can become grayish white, thickened and hardened, with a coarse and astringent feeling when licking with the tongue. If the oral mucosa white spot thickens rapidly, cracks, bleeding and hardening of the basal part, it should be considered whether it is cancerous or not. Oral erythema: It is not as common as oral white spots, but the cancer rate is 85%. Erythema is a bright red and soft plaque on the oral mucosa that is flat or slightly concave on the surface of mucosa, with clear boundary with normal mucosa, which is usually found on the floor of the mouth, tongue, cheek, gums and palate. Patients may have slight pain or discomfort or no symptoms at all. Once the erythema bleeds, hardens and ulcerates, it is a sign of cancer. Oral lichen planus: Oral lichen planus is a more common oral mucosal lesion, which usually occurs on the cheek and tongue. If vesicular lichen planus does not heal for a long time and there is granular hyperplasia, there is a possibility of malignant transformation, which must be confirmed by pathological section. How to prevent and control oral precancerous lesions 1. Reduce the local stimulation of the mouth. Use soft toothbrush to brush teeth; do not eat spicy and irritating food; do not smoke and drink less alcohol; strengthen oral hygiene and regular oral cleaning; correct unsuitable dentures. 2, treatment of persistent mouth ulcers. Timely supplement vitamins; do not abuse antibiotics for a long time to cause Candida albicans infection. 3.Pay attention to check whether there are precancerous lesions in the oral cavity. 4.Regular examination and histopathological biopsy should be done for clear diagnosis if high risk signs are found.