Leukoplakia refers to white or grayish white keratotic lesions that occur only on the mucosa. Such plaques on the oral mucosa cannot be wiped off and cannot be classified as other diseases in clinical and histopathological terms. It is a common non-infectious chronic disease. It can occur in all parts of the oral mucosa, but most of them occur in the cheeks and tongue. The prevalence rate in the 1980 census in China was 10.47% (including smoke stains). For a long time, white patches on the oral mucosa have been called "leukoplakia", which has confused many white lesions with leukoplakia, resulting in inappropriate results in epidemiology and treatment methods. In addition to white, the color of leukoplakia can also be mixed with red and white lesions. It should be clear that leukoplakia is a clinical term seen by the naked eye. The changes in histopathology should meet the characteristics of precancerous lesions - abnormal epithelial hyperplasia, rather than simple epithelial hyperplasia.