Ankylosing spondylitis is a chronic inflammatory disease that is classified as a rheumatologic-immunologic disease. Lumbar fasciitis is a sterile inflammatory disease of the fascia and muscle tissue of the lumbar back caused by various factors. These are two different diseases. The cause of ankylosing spondylitis is still unclear, and it is currently believed to be related to a number of factors such as genetics, infection, environment and immunity. The disease starts slowly and insidiously, and in the early stage, dull pain may appear in the lumbosacral joints with morning stiffness, waking up in the middle of the night with pain and difficulty in turning over, which will be alleviated after activities. With the progression of the disease, symptoms such as limited joint movement and spinal deformity can gradually appear. Imaging results can assist in the diagnosis. The sacroiliac joints can be seen to have lesions such as narrowing of the joint space. Lumbar dorsal fasciitis refers to pathological changes in the soft tissues of the lumbar back, triggered by cold, dampness, chronic strain, etc. Edema, exudation and fibrous changes occur in the fascia and muscle tissues of the lumbar back. The main manifestations are diffuse dull pain, soreness, swelling and widespread pressure pain in the low back. It is usually severe in the morning, less severe during the day, and then worse in the evening. Imaging tests usually have no positive findings. Ankylosing spondylitis and lumbar back fasciitis are two diseases of different nature and are treated differently due to different causes. If you experience low back pain, it is recommended to go to the hospital in time to identify the cause and give appropriate treatment.