Myositis ossificans is a rare, benign, solitary and self-limited disease, characterized by non-neoplastic ectopic bones in soft tissue or skeletal muscle, most commonly in humerus, quadriceps femoris and adductor muscle group, with or without a history of external injuries. The main manifestations of this disease are local pain and swelling, loss of range of motion, and X-ray examination is one of the important means to diagnose myositis ossificans. Most patients can be treated conservatively with good results. For persistent symptoms or progressive cases, surgical resection can also be selected. In this paper, a progressive child case is introduced, and the clinical features, X-ray manifestations and treatment methods of the patient are discussed in order to improve the reference for the diagnosis and treatment of myositis ossificans.