Morphine is the main drug for the treatment of moderate to severe cancer pain. Since WH0 proposed the principle of three-step analgesia in 1982, the global consumption of morphine has increased rapidly through more than 20 years of efforts. The medication situation of cancer pain patients in China has also greatly improved, and the annual morphine consumption has increased more than 10 times in 20 years. Nevertheless, compared with western developed countries, China is still far behind. Due to the influence of many factors, only 40% of cancer pain patients in China can get effective relief, and more than 70% of advanced cancer patients still have pain, of which more than half of them endure the torture of severe pain. These factors include insufficient understanding by medical personnel of the principles of cancer pain treatment and the individualized characteristics of opioid dosage. Medical personnel, in general, should start from the following three aspects to improve the understanding of standardized treatment of cancer pain. Correct assessment of cancer pain Assessment of cancer pain is the key to treating cancer pain. Understand the site, nature and degree of pain etc. through assessment. Adjust the dose of opioids through regular reassessment: if the pain level is ≥7 points, the dose is increased by 50%-100%; if the pain level is 5-6 points, the dose is increased by 25%-50%; if the pain level is ≤4 points, the dose is increased by 25%. Pain intensity was assessed while differentiating the nature of the pain. For neuropathic pain, on the basis of conventional pain medication, the adjunctive application of gabapentin, pregabalin, tricyclic antidepressants will further improve the efficacy. Timely prevention and treatment of side effects of painkillers Opioids used for cancer pain treatment are mainly controlled and slow-release dosage forms, whose constant release rate can control the effective concentration of the drug in the body relatively stable and duration, the adverse effects are significantly reduced compared with immediate-release drugs, and the “addictive properties” are so low as to be negligible, which has become the mainstream of cancer pain treatment. The more common and less tolerable adverse effect of opioids is constipation, which can be intervened with lactulose or phenolphthalein, either prophylactically or therapeutically. The next most common reactions are nausea and vomiting, which are more likely to occur in patients on initial therapy; this reaction is usually tolerated within a week, and administration of metoclopramide prophylactically or therapeutically will increase patient compliance. Standardized titration emphasizes individualized dosing There are significant individual differences in opioids. For example, the dose of morphine sulfate controlled-release tablets required for the same level of pain may fluctuate between 10 and 600 mg. Because opioids do not have a ceiling effect, a full dose should be given whenever the patient needs it, according to the principle of dose titration, to achieve optimal analgesia and duration of analgesia. During the period of constant dosing, if there are more than three outbreaks of pain per day, or the duration of analgesia is shorter than the regular duration, the dose of constant dosing should be increased according to the principle of incremental increase (usually controlled and extended-release opioids) rather than increasing the number of dosing. The safety of applying high doses of opioids in patients with moderate to severe cancer pain has been widely reported. Bercovitch et al. from Israel retrospectively analyzed the data of 453 patients with cancer pain in 1996-1997 and found that 12.14% of patients required morphine at a dose of more than 300 mg/d, and 8% required more than 600 mg/d of morphine for effective control of cancer pain. The results of safety analysis confirmed that high-dose morphine had no effect on the survival of the patients, and the patients did not suffer from life-threatening adverse reactions such as respiratory depression or mental dependence. In China, Fang Rong and Wang Bing reported cases of oral morphine sulfate controlled-release tablets with a dosage of more than 1,000 mg/d, which did not cause adverse reactions such as drowsiness and respiratory depression while controlling pain better. Therefore, there is no need to have fear of high dose morphine. The guideline for clinical application of narcotic drugs issued by the Ministry of Health in 2007 clearly stipulates: “There is no extreme limit on the long-term use of opioid analgesics (e.g., morphine) in advanced cancer, i.e., the dosage should be decided according to the individual’s tolerance level of opioid analgesics, such as morphine, but close attention should be paid to the monitoring of adverse reactions. Injectable prescriptions should not exceed 3 days of dosage at one time, controlled (extended) release preparations should not exceed 15 days of dosage at one time, and other dosage forms of narcotic drugs should not exceed 7 days of dosage at one time.” Clinicians should prescribe adequate amounts of medications, including controlled extended-release morphine preparations and immediate-release morphine for eruption pain control, as well as medications for the prevention or treatment of side effects, as long as they are needed by the patient, in order to provide good control of pain while decreasing the side effects of the medication and improving the patient’s quality of life.