Common causes of leg pain in children aged 3 to 12 are growing pains, femoral head dysplasia or hip dislocation, localized arthritis or certain systemic immune disorders. Specific treatment should be implemented according to the cause of the disease. 1. Growing pains: mainly at night, mostly occurring in children aged 5 to 12 years old, may be related to vitamin deficiency, excessive activity, local cold and other factors. Therefore, we should pay attention to local warmth, can be improved by oral calcium or vitamin D, and can be more sunshine to promote the body’s vitamin D synthesis. 2. Dysplasia of the femoral head or hip dislocation: it is necessary to carry out hip x-ray in time to make a clear diagnosis, and conservative treatment or surgery can be used if the diagnosis is confirmed. 3. Localized arthritis or certain systemic immune diseases: redness, swelling, heat and pain in the joints often occur, and the hospital should do the relevant immune examination in time, and if diagnosed, the cause of the disease needs to be treated, such as the use of penicillin and other antibiotics and other treatment methods. 3~12 years old children leg pain is recommended to timely medical treatment, a comprehensive examination, under the guidance of the physician for the cause of treatment, so as not to delay the condition.