Pain is an unpleasant sensory and emotional experience, accompanied by present or potential tissue damage, and is a common symptom of cancer. According to the World Health Organization (WHO), the proportion of cancer patients with pain is 30% to 50% worldwide, and 60% to 90% for patients with advanced disease. Pain affects patients’ activities, emotions, quality of life and compliance with treatment, and has gradually become a focus of medical attention. WHO recognized pain as a priority problem worldwide in 1986 and has been making it one of its priorities. The control of cancer pain should be based on aggressive pain management, starting at the early stage of cancer diagnosis and continuing throughout the course of the disease, rather than just palliative care for advanced cancer. At present, the formal pharmacological treatment for cancer pain is the three-step analgesic therapy for cancer pain proposed by WHO, which includes the following five basic principles: 1.Dosing according to the step: non-opioid (aspirin, anti-inflammatory pain, paracetamol, naproxen, etc.), weak opioid (codeine, tramadol, oxycodone, dextropropoxyphene, etc.), strong opioid (morphine, fentanyl, methadone, dihydromorphone, etc.), and pain management. The non-opioid pain medications can be combined with weak and strong opioids in the second and third steps to increase their efficacy. In addition, all three steps can be combined with adjuvant drugs according to the pathophysiology of pain, such as: corticosteroids prednisone, dexamethasone, etc., antidepressants amitriptyline, Prozac, etc., anticonvulsants phenytoin sodium, carbamazepine, etc. 2.Non-invasive drug delivery: Most patients can relieve cancer pain through oral drug delivery. Oral drug delivery is simple, convenient, non-invasive and conducive to long-term drug use. The peak of oral blood concentration of opioid drugs appears late and is not easy to produce drug dependence. Patients who have difficulties in oral administration can choose to take drugs under the tongue, anal plugs, vaginal administration or transdermal patches. 3. Timely dosing: The medication should be given at intervals according to the effective action of the drug to maintain the stability of the blood concentration in the patient’s body so that the pain can be relieved continuously. 4.Individualization of medication: The dose of opioids varies greatly among individuals, and should be administered on an individual basis, titrating the dose so that pain can be effectively controlled without major side effects. 5.Pay attention to specific details: pay close attention to the patient’s reaction after the application of painkillers, in order to obtain the effect while minimizing the side effects. By following the 5 basic principles of three-step pain relief therapy, we can surely achieve the goal of “making cancer patients pain-free” as proposed by WHO.