Painful oral ulcers should be considered as oral cancer first. Many oral cancers manifest as ulcers with infiltrative growth, hard lumps can be touched at the base and around the ulcers, with raised and uneven edges and depressions in the middle, granular bumps on the depressed surface covered with necrotic tissue, and spontaneous pain when invading the nerves. Due to the growth of cancer, compression and invasion of nerves, corresponding neurological symptoms will appear. For cancer in the jaw bone, the earlier symptoms may be severe and continuous pain, numbness of lower lip, etc. If the above painful symptoms occur you should seek treatment at the Maxillofacial Surgery Department of the Dental Hospital as a matter of urgency. Recurrent aphthous ulcers are the most common ulcerative damage in the oral mucosa. Aphthous ulcers have the clinical characteristics of “yellow, red, concave and pain”, i.e., the lesion surface is covered with yellow pseudomembrane, surrounded by a congested red halo band, with a central depression and obvious burning pain. Especially in herpes-like aphthous ulcers, the number of ulcers is large. When the mouth ulcer is painful, the treatment can be mainly localized: anti-inflammatory, pain relief, prevention of secondary infection, and promotion of healing. Local pain medication can be used for pain. Such as: lidocaine gel, spray and benzocaine gel, etc. For specific medication, please refer to the clinical situation and be guided by the doctor’s interview.