The symptoms of cancerous oral ulcer are mainly manifested in the following aspects: Firstly, cancerous oral ulcer, its patients will show oral mucosa erosion, congestion and edema, the lesion shows central depression and edge elevation, the patients will have obvious pain, swelling and discomfort and other symptoms. Secondly, cancerous oral ulcers, which are easy to be ignored at first, have poor effect after medication or persist, with the aggravation of symptoms or prolongation of time, their oral ulcers are deeper and have harder edges, and the nature of lesions can be clarified after surgical excision or biopsy for pathological examination.