Pain is the most common sensory experience, and is felt wherever there are nerve endings. Pain is also a protective sensation to avoid further injury. The most common causes of pain are the following: first, trauma, trauma to various parts of the body can cause pain, and patients can also be accompanied by local redness, swelling, bleeding, increased local temperature and dysfunction. Second, infection, various causes of infection can be accompanied by pain, such as urinary tract infection, acute gastroenteritis, peritonitis, pleurisy, intracranial infection, etc. Third, chronic muscle strain, patients with prolonged heavy physical activity can develop muscle strain, which in turn leads to muscle pain and discomfort. Fourth, occupying lesions, most commonly in patients with advanced malignant tumors. The cause of pain should be analyzed according to the location, nature, duration of pain, degree of pain and accompanying symptoms, etc. It is recommended to go to the hospital.