At present, the 5-year survival rate of oral and maxillofacial cancer patients is about 60%, which is not satisfactory yet. The reason for this is that cancer treatment is now a “post-cancer treatment”, that is, after the cancer has already formed. If some precursor changes in cell morphology or biochemical markers of cancer can be detected before the formation of cancer, active treatment can be carried out to interrupt the cancer process at the pre-cancerous stage, and good results can be received. The prevention of cancer can be divided into three levels: Level I prevention is etiological prevention, which is the most fundamental measure to reduce the incidence rate; Level II prevention is mainly to carry out three early measures, namely: “early detection, early diagnosis and early treatment”, in order to improve the cure rate; Level III prevention refers to the treatment and therapy of patients, whose goals are to cure the tumor, prolong life expectancy, reduce pain and prevent recurrence. The objectives are to cure the tumor, prolong life expectancy, reduce pain and prevent recurrence. According to the above concepts, the prevention of oral and maxillofacial cancer includes the following elements: (1) Eliminate or reduce cancer-causing factors. The best prevention method is to eliminate the cause of the disease. The prevention of oral and maxillofacial tumors should eliminate external chronic irritants, such as timely treatment of root, crown and misaligned teeth, as well as grinding sharp tooth tips, removing bad restorations and bad partial or complete dentures, so as to avoid frequent damage and irritation of oral mucosa and thus avoid inducing cancer, especially tongue, cheek and gum cancer. Pay attention to oral hygiene and do not eat foods that are too hot and irritating. In these aspects, oral preventive health care is one of the measures to prevent oral cancer. In addition, quitting smoking and alcohol; strengthening protective measures when working under outdoor exposure or exposure to harmful industrial substances; avoiding excessive mental tension and depression and maintaining optimism are all significant in preventing the occurrence of tumors. (2) Timely treatment of precancerous lesions. According to the recommendation of WHO (1972), the definition of precancerous lesion is: “a morphologically altered tissue which has a greater potential for cancer than the corresponding normal-looking tissue”. Therefore, timely management of precancerous lesion is an important part of preventing and interrupting the development of oral and maxillofacial carcinoma. At present, the understanding of precancerous lesions is not fully unified. Some pathologists divide precancerous lesions into three categories: super precancerous lesions (carcinoma in situ and intraepithelial carcinoma), true precancerous lesions (including interstitial and proliferative lesions) and potential precancerous lesions (still benign histological changes, but may become cancerous). According to clinicians, super precancerous disease is in fact cancerous and should not be considered as precancerous lesion; true precancerous disease is clinically referred to as precancerous lesion; and potential precancerous lesion refers to precancerous condition. According to the WHO recommendation (1972), precancerous condition is defined as “a general condition that significantly increases the risk of developing cancer”. From a clinical point of view, both precancerous lesions and precancerous states should be given due attention because they are both capable of developing cancer, but the differences in incidence and timing are only different. The most common precancerous lesions on the oral and maxillofacial surfaces are leukoplakia and erythema. Oral mucosal leukoplakia is considered to be one of the most common precancerous lesions. The cancer rate of leukoplakia has been reported in the literature, ranging from less than 1% in the low cases to 60% in the high cases, and about 5% in the general tract. In recent years, there are many reports in the literature that the cancer risk of erythema is especially higher than that of leukoplakia, thus generally attracting the attention of clinical workers. Clinically, it is found that 80% of the erythema patients are confirmed to be invasive carcinoma or carcinoma in situ by pathological section. For the clinical manifestations and diagnostic criteria of white spots and erythema, please refer to Oral Mucosal Pathology. Common precancerous states of the oral and maxillofacial region are considered to be oral lichen planus, oral submucosal fibrotic lesions, discoid lupus erythematosus, epithelial hyperkeratosis, congenital dyskeratosis, and syphilis and staining dry skin disease. For the flat moss, especially the vesicular type and atrophic flat moss who cannot be cured for a long time, should be fully alert, according to the literature, the malignant rate of flat moss is about 1%~10%. (3) Strengthen the propaganda of cancer prevention. The public should be made to understand the danger of cancerous tumors and raise their vigilance against them; so that they can understand some knowledge of cancer prevention. Such as: recognize the characteristics of precancerous lesions and early symptoms; when there is suspicion, examination should be conducted to detect tumors in time for early treatment; pay attention to oral hygiene, do not eat too hot and stimulating diet, ensure appropriate nutrition, and quit bad habits such as smoking and alcohol. The occurrence of many cancers is related to the aging of the body and chronic diseases, and mass sports activities can prevent the aging of the body and reduce diseases. Therefore, strengthening physical exercise is also of certain significance to prevent the occurrence of tumors. (D) Carry out cancer prevention census or monitoring of susceptible people. Early malignant tumors can be cured, but the treatment effect is very poor when it reaches advanced stage. Early stage tumors are easy to be ignored because the symptoms are not obvious or similar to the symptoms of related diseases. Taking cancer prevention survey can detect cancer tumor early, diagnose it early and get early and effective treatment, which is an important aspect of current cancer prevention work. The occurrence and development of tumors take a certain period of time, usually several years or even longer. Many cancer tumors tend to develop slowly in the early stage and develop rapidly only in the later stage, which indicates that most malignant tumors are possible to be detected early. Timely diagnosis and early treatment are also the most effective measures to improve the cure rate. Cancer prevention screening should be carried out among the high incidence or susceptible people, rather than blindly, to obtain the maximum benefit. After people with suspicious symptoms are found, further examinations are conducted to determine the presence of tumors and to treat the cancer and early cancer patients found. Cancer screening is usually conducted once every 3 to 5 years. Another way is to open a specialized outpatient clinic for oral and maxillofacial tumors in hospitals, which specializes in examining and finding suspected cases and treating patients with diagnosed tumors, including supervised follow-up of children of patients with tumors with obvious genetic factors. It is best to have regular checkups, one to two times a year. Cancer examination can not only achieve early detection and timely treatment, but also accumulate information for exploring the incidence and causes of tumors, so as to take more effective measures for future tumor prevention. International experience proves that stomatologists or dentists should have the inescapable obligation to detect early oral tumor lesions in the daily consultation and treatment of oral diseases.