With the development of society, the pressure of people’s life and work increasing, and the change of environment, the incidence of malignant tumors has a tendency to increase, and so does oral cancer. In recent years, many patients mistakenly suspect benign oral lesions or normal structures as oral cancer or precancerous lesions. In order to reduce the mental pressure and the time and economic burden of patients, several situations in which patients are easily suspected of oral malignant tumors are briefly described and explained. Recurrent oral ulcers; they are characterized by recurrent episodes, the location of the disease is not fixed, and the ulcers in the same location usually heal in about one week, and no malignant cases have been seen in this situation. However, it should be noted that, the same location of the ulcer for more than two weeks does not heal, the periphery of the hard, crater-like, and have a tendency to expand and so on, should immediately go to the hospital to check whether the malignant change.