After radiation therapy for parotid cancer, the joints and muscles are irradiated with certain radiation dose, the symptoms of fibrosis will appear, resulting in the reduction of muscle extension, limiting the movement of joints, and in serious cases, it will lead to the inability to open the mouth and unable to eat, so patients have to carry out active mouth-opening exercises after radiation therapy for parotid cancer. It takes a long time for patients to have difficulty in opening mouth after radiotherapy for parotid cancer, it is a gradual process, which will appear unconsciously, and once it occurs, it will be difficult to recover, so it is necessary to carry out active mouth opening exercise. You can put the cork of hot water bottle or peel potatoes into a wedge shape and put it in the mouth to make sure that the degree of opening the mouth is a little bit difficult and within the tolerance range, and mark it well every time to make sure the degree of opening the mouth every time. When patients undergo radiotherapy for parotid cancer, they must actively conduct mouth opening training under the guidance of doctors to promote recovery.