Left posterior back pain is related to stomach ulcer in some way, but it may also be due to the presence of other conditions, such as lumbar muscle strain, kidney stones, and strenuous exercise. Left posterior back pain may be caused by gastric ulcer. Some patients with gastric ulcer may have radiating left posterior back pain, which is related to inaccurate localization of visceral nerves. Typical symptoms of gastric ulcer are stomach pain, acid reflux, vomiting blood and black stool. Among them, stomach pain mostly occurs after meals, lasts for several minutes or hours, and reappears after the next meal. Left posterior back pain may be related to lumbar muscle strain, kidney stones, lumbar intervertebral disc herniation, female pelvic inflammatory disease and uterine inflammation and other diseases. Left back pain can also be triggered by prolonged sitting and strenuous exercise. Whether the left posterior back pain is caused by gastric ulcer, it is recommended to consult a doctor with medical history, symptoms and auxiliary examination to clarify.