Cancer patients may feel pain at night, which is mainly related to sleeping posture, diet, and environmental and psychological factors. 1.Sleeping posture can cause night pain in cancer patients. During sleep, the compression effect of the body and the involuntary activities during sleep can cause direct stimulation to the cancer site leading to pain. Some malignant tumors of limbs and torso near the bed can cause pain due to direct compression, and also can cause pain and discomfort due to collision or stimulation to these parts during turning over. 2.Dietary factors also have influence on cancer pain. Gastrointestinal tumors, eating too much at dinner, can cause excessive secretion of gastric acid, increased intestinal peristalsis and increased intestinal tolerance tension due to the difficulty of digesting the food itself, which can cause pain and discomfort. In particular, some cancers of the gastrointestinal tract are extremely prone to this problem. Tumors in these parts can have digestive dysfunction in itself, in addition, gastrointestinal tract tumors are mostly accompanied by decreased cavity volume caused by tumor growth, and the amount of dietary discomfort leads to the difficulty of food digestion, and the dinner time is close to the sleeping time, so it will aggravate this problem and lead to pain and discomfort at night. 3, In most patients, the response to persistent pain is autonomic. At night, the environment is relatively quiet, the patient’s external stimulation will be relatively reduced, and the patient will pay too much attention to his/her own physical sensation because of the reduction of mental and physical strength caused by cancer pain. A patient whose pain is not obvious during the daytime may obviously feel the pain and discomfort caused by cancer at night. Sometimes, not only pain, but also irritability and depression may occur. Especially patients with liver cancer, pancreatic cancer and gastrointestinal tumors with symptoms of intestinal obstruction may show very bad mood. Cancer patients may feel the pain more obviously at night. Therefore, family members need to be more attentive at night and pay attention to the patient’s changes during this time.