The principles of pain relief for cancer are generally based on the three-step pain relief principle developed by the World Health Organization, or WHO. The three-step pain relief principle means that it is okay to start using non-steroidal mild painkillers if they can stop the pain. If it does not stop the pain, you need to switch to medium-acting opioid painkillers that belong to the weak opioid class, such as codeine or tramadol extended-release tablets, etc. If the pain still does not stop, a strong opioid, such as oxycodone or morphine, can be used. However, there are new principles of pain relief, and it is considered possible to use strong opioid drugs directly, especially for some patients with advanced malignant tumors, to stop the pain and reduce the patient’s suffering. In addition, the application of pain medication needs to be mainly oral. If oral administration is not possible, intramuscular injection or some transdermal patches can be considered.