When some teenagers tell their families about “back pain”, they often get this answer: “Children have no back, so they will have back pain, sleep overnight and it will be fine” In the daily habit of thinking, back pain is a disease only for adults. In fact, there is a disease called ankylosing spondylitis, which occurs in more than 90 percent of young men and can cause serious spinal deformities. Ankylosing spondylitis is a chronic progressive inflammatory disease that mainly affects the sacroiliac joints, spinal prominences, paraspinal soft tissues and peripheral joints, mostly in adolescent men aged 15-30 years (11 times more men than women). The early manifestations are stiffness, soreness and drowsiness of the lower back, with pain evident at night and early in the morning, aggravated by prolonged sitting and standing, and relieved by activity. Some patients also have swelling and pain in the hip, knee and ankle joints, hip and groin pain, dull pain in the back of the neck, red eyes, heel pain, low fever and weakness. Because of the slow progression of the disease, which begins with intermittent back pain and mild systemic symptoms and develops persistently only after several months or years, early patients with ankylosing spondylitis are often overlooked or misdiagnosed. With the further development of the disease, the patient develops a “duck walk”, posterior hip bulge, flat back, and even hunchback, lumbar spine and hip joint movement restrictions, resulting in the inability to take care of themselves, loss of labor force, disability rate of more than 30%. Due to the special symptoms of this disease, it is often misdiagnosed as rheumatoid arthritis, lumbar disc herniation, sciatica, joint tuberculosis, synovitis, osteophytes and other diseases. The cause of this disease, modern medicine has not found a clear answer, most believe that it is related to genetics, infection, environmental factors, immunity, etc. Therefore, in the treatment, the main use of drugs and functional exercise, and late stage can be corrected by surgery. The prognosis of this disease is good or bad, early diagnosis and early treatment is the key. X-ray examination is of great importance to the diagnosis of this disease. 98%-100% of cases have X-ray changes of the sacral joint, which is an important basis for the diagnosis of this disease. In early suspected patients, HLA-B27 (histocompatibility antigen B27) determination should be done, if it is positive, it will help to confirm the diagnosis at an early stage. There are also some other diseases that can cause low back pain in adolescents that need to be ruled out, such as lumbosacral joint strain, tuberculous spondylitis, and Ritter syndrome. Adolescence is an important period of growth and development, and it is also the most stressful period of study and life. Being reluctant to mention the back pain that occurs intermittently or continuously or being ignored by family members after mentioning it is detrimental to early diagnosis and treatment. We would like to remind everyone that adolescents’ low back pain should be diagnosed and treated in a timely manner so that they can have a healthy body.