Cancer pain assessment is a prerequisite for rational and effective pain management. Cancer pain assessment should follow the principles of “routine, quantitative, comprehensive and dynamic” assessment. (1) Routine assessment principle. Routine assessment of cancer pain means that medical and nursing staff should take the initiative to ask cancer patients whether they have pain, routinely assess their pain conditions and make corresponding medical records, which should be completed within 8 hours after admission. For cancer patients with pain symptoms, pain assessment should be included in the content of nursing routine monitoring and recording. Routine pain assessment should identify the causes of explosive episodes of pain, such as pain due to pathological fractures requiring special management, brain metastases, infections, and acute conditions such as intestinal obstruction. (b) Principle of quantitative assessment. Quantitative assessment of cancer pain refers to the use of quantitative criteria such as pain level assessment scale to assess the patient’s subjective pain level, which requires close cooperation from the patient. When quantitative assessment of pain, it should focus on the most severe and least severe pain level of patients in the last 24 hours, as well as the pain level of usual conditions. The quantitative assessment should be completed within 8 hours of the patient’s admission to the hospital. Quantitative assessment of cancer pain usually uses three methods: numerical rating scale (NRS), facial expression assessment scale, and pain rating of complaints (VRS). 1.Numerical Rating Scale (NRS): The Numerical Rating Scale of Pain Level (see Figure 1) is used to assess the pain level of patients. The degree of pain is indicated by 0-10 numbers in order, with 0 indicating no pain and 10 indicating the most severe pain. The patient chooses a number that best represents his or her pain level, or the healthcare provider asks the patient: How severe is your pain? The healthcare provider selects the corresponding number based on the patient’s description of the pain. The pain level is classified according to the number corresponding to the pain: mild pain (1-3), moderate pain (4-6), and severe pain (7-10). 2.Facial expression pain rating scale method: Pain assessment is performed by the health care personnel according to the patient’s facial expression status during pain, compared with the Facial Expression Pain Rating Scale (see Figure 2), which is applicable to patients with expression difficulties, such as children, the elderly, and patients with language or cultural differences or other communication barriers. 3.Subjective pain grading method (VRS): according to the patient’s complaints of pain, the pain level is divided into three categories: mild, moderate and severe. (1) Mild pain: painful but tolerable, normal life, no disturbance in sleep. (2) Moderate pain: pain is obvious and unbearable, requiring analgesic drugs and disturbed sleep. (3)Severe pain: pain is severe and unbearable, analgesic drugs are required, sleep is severely disturbed, and may be accompanied by autonomic disorder or passive body position. (3) Principle of comprehensive assessment. Comprehensive assessment of cancer pain refers to the comprehensive assessment of cancer patients’ pain condition and related conditions, including the cause and type of pain (somatic, visceral or neuropathic), pain episodes (nature of pain, aggravating or relieving factors), pain relief treatment, function of vital organs, psycho-spiritual condition, family and social support, and past history (e.g. history of psychiatric disease, history of drug abuse), etc. The first comprehensive assessment should be conducted within 24 hours after the patient is admitted to the hospital, and during the treatment process, another comprehensive assessment should be conducted within 3 days of giving pain relief treatment or when stable remission is achieved, in principle no less than 2 times/month. Comprehensive assessment of cancer pain usually uses the Brief Pain Assessment Inventory (BPI) (see Annex 1) to assess pain and its impact on patients’ mood, sleep, mobility, appetite, daily life, walking ability, interaction with others and other quality of life. Patients should be valued and encouraged to describe their needs and concerns about pain management, and to set goals for optimizing patient function and quality of life based on their condition and wishes for individualized pain management. (iv) The principle of dynamic assessment. Dynamic assessment of cancer pain refers to continuous and dynamic assessment of changes in pain symptoms of cancer pain patients, including assessment of changes in pain level and nature, explosive pain episodes, factors of pain reduction and aggravation, and adverse reactions to analgesic treatment. Dynamic assessment is especially important for dose titration of drug analgesic treatment. The type and dose titration of medication, pain level, and changes in condition should be recorded during pain management.