Cancer pain is one of the main causes of suffering for patients with advanced cancer. The causes can be divided into three categories: pain directly caused by tumor, accounting for about 88%; pain caused by cancer treatment, accounting for about 11%; and pain indirectly caused by tumor, accounting for about 1%. Clinically, there are also a few tumor patients who can have pain unrelated to tumor, for example, lumbar and leg pain caused by lung cancer patients who also suffer from disc herniation, so the causes of pain in cancer patients must be clearly diagnosed. Cancer pain is generally treated mainly by medication, and surgical treatment often needs to be considered in conjunction with the overall physical condition and survival of the patient. 1. Principles of drug treatment for cancer pain (1) Try to administer drugs orally for long-term use, which can reduce dependence and addiction. (2) Give drugs regularly and on time instead of giving drugs when pain occurs. (3) Give the medication according to the step, according to the “three-step therapy” recommended by WHO for cancer pain. (4) The medication should be individualized. (5) Pay attention to the use of anxiolytic, antidepressant and hormonal drugs, which can improve the effect of analgesic treatment. (2) The “three-step therapy” of cancer pain medication (1) The first step: non-opioid analgesics. Used for patients with mild cancer pain, the main drugs are aspirin, acetaminophen, etc. Adjuvant drugs can be applied as appropriate. (2) Second ladder: weak opioid analgesics. The main drugs include codeine, which is generally recommended to be used together with the first-tier drugs because the mechanism of action of the two drugs is different. The first-tier drugs mainly act on the peripheral nervous system, while the second-tier drugs mainly act on the central nervous system, and the combination of the two can enhance the analgesic effect. Adjuvant drugs can also be used as needed. (3) Third step: strong opioid analgesics. It is used for the treatment of moderate or severe cancer pain, and is used when the drugs of the first and second steps are ineffective.