Left back rib pain is commonly caused by intercostal neuritis, rib fracture and lung cancer and other diseases invading the posterior chest wall. 1. Left intercostal neuritis: Thoracic spine disease, ankylosing spondylitis, herpes virus infection and other diseases can compress or stimulate the intercostal nerves, resulting in pain, which is distributed from the left side of the back along the intercostal space in a semi-circular (band-like) manner in the forward direction, and manifests itself as a burning pain or tingling in one or two rib regions. 2. Left posterior rib fracture: the patient usually has the history of trauma, the pain in the back is more intense, and there is pressure and squeezing pain at the rib fracture. 3. Invasion of posterior chest wall by lung cancer: invasion of posterior chest wall by lung cancer can stimulate the pain of nociceptive nerve endings and intercostal nerves in the wall pleura and periosteum of ribs as well as muscle tissues, and the pain is more intense and lasting. With left back rib pain, it is recommended to go to the hospital for further diagnosis and treatment in time.