A precancerous lesion is defined by the World Health Organization (WHO) in 1972 as a tissue that is morphologically altered and has a greater likelihood of developing cancer than its correspondingly normal appearance. The most common precancerous lesions of the oral and maxillofacial region are leukoplakia and erythema. Oral mucosal leukoplakia is considered as one of the most common precancerous lesions, and its cancer rate is reported in the literature, ranging from less than 1% in the low cases to 60% in the high cases, generally reported to be around 5%. In recent years, many scholars have suggested that the risk of carcinoma of erythema is especially higher than that of leukoplakia. Clinically, it is found that 80% of the pathological sections of erythema patients are confirmed to be invasive carcinoma or carcinoma in situ, thus generally attracting the attention of clinicians. In addition, some common mucosal diseases of oral cheek such as oral lichen planus, oral submucosal fibrosis, discoid lupus erythematosus, epithelial hyperkeratosis and congenital dyskeratosis have been positioned as “precancerous state” by WHO, especially vesicular and atrophic lichen planus, whose malignant rate is about 1% to 10%. At present, scholars believe that timely treatment of precancerous lesions is an important part of preventing and interrupting the occurrence of oral and maxillofacial carcinomas. The treatment measures include: 1, strengthen the propaganda of cancer prevention, the public understand the danger of cancer tumor, raise the importance of precancerous lesions, recognize the characteristics and early symptoms of precancerous lesions; when there is a suspicion, especially the elderly patients should be timely examination, regular follow-up, to achieve early prevention, early detection and early treatment. 2.Keep oral hygiene, quit smoking and alcohol, eat less hot and stimulating food, and ensure reasonable nutrition. 3.Treat the residual roots, residual crowns and misaligned teeth in the mouth in a timely manner, as well as grind down sharp tooth tips and remove bad restorations and bad dentures, so as to avoid frequent damage and stimulation of oral mucosa, which can avoid inducing cancerous tumors. Avoiding long-term excessive mental tension, moderate physical exercise and improving one’s immunity and resistance are all important to prevent precancerous lesions and tumor occurrence.