Cancer pain is a sensation caused by the transmission of information to the nerve center about the need to repair or regulate the pain site, alias, cancer pain, advanced cancer pain, and is one of the main causes of pain in patients with advanced cancer. Among the pain patients, 50% to 80% of pain is not effectively controlled due to various reasons. So what are the causes of cancer pain? The following are the causes of cancer pain: 1. direct compression and stimulation of nerves by tumor; 2. skeletal metastasis of tumor; 3. stimulation of pain-sensitive tissues (blood vessels, lymphatic vessels, etc.) by tumor; 4. pain caused by tumor secretion factors, pain caused by accompanying inflammatory factors; 5. pain after surgery, radiation therapy, chemotherapy and other treatments; 6. psychological factors. The treatment of advanced cancer pain is mainly to control or relieve pain, improve quality of life, restore patients’ normal life as much as possible, improve patients’ mobility, prolong pain-free period and realize patients’ expectation.