The back hurts at night and gets better during the day. The following reasons should be considered when this happens: First, non-disease reasons: it may be that the bed chosen is soft, and the thoracic spine will sink during sleep and the physiological curvature will change. At this time, the muscles of the back and the vertical spinal muscles on both sides of the thoracic spine will be under greater stress, so when you wake up, you will show back pain. Second, the cause of the disease: to consider ankylosing spondylitis, ankylosing spondylitis will appear when the back pain, pain at night is more obvious, many patients will even wake up in the night pain. This pain can be improved by moving the thoracic and lumbar joints when you get up in the morning. The specific differential diagnosis must be made by going to the hospital for X-rays as well as HLA-B27 index examination, combined with the patient’s specific medical history, to finally arrive at a judgment.