Pain in the left iliac region may be caused by physiological factors such as sitting incorrectly or excessive weight bearing. It may also be caused by some pathological factors, such as hip joint lesions, lumbar spine lesions, rheumatoid immune diseases, trauma, and bone occupation. It is necessary to consult the doctor in time to find out the cause of the disease. 1. Physiological factors: when sitting improperly or overweight, the left iliac due to the load borne by the larger, may cause local pain symptoms, through adjusting the sitting posture, rest and hot compresses and other lifestyle modification, more can be improved. 2. Hip joint lesions: when there is hip synovitis, femoral head necrosis, acetabular dysplasia, due to local aseptic inflammation or ischemia and other changes, it will involve the left iliac, causing pain. 3. Lumbar spine lesions: when there is disc herniation, spinal stenosis or lumbar spine slippage, due to the compression of the nerve root or spinal canal, it will also radiate to the left iliac region and cause pain. 4. Rheumatic immune disease: the most common is ankylosing spondylitis, which can cause sacroiliac joint lesions, spinal fusion, etc., and also lead to left iliac pain. 5. Trauma: when the left iliac is overstretched or violently injured, it will cause local soft tissue and bone damage and cause pain. 6. Bone occupation: when there is a tumor or bone cyst in the left iliac region, it will invade the bone or compress the surrounding tissues, thus causing pain. To sum up, when the left iliac pain occurs, we should exclude physiological factors, timely consult the doctor to find out the disease, and should follow the doctor’s instructions to standardize the treatment.