Osteosarcoma is a malignant tumor that occurs in adolescent bone, commonly found in the distal femur, proximal tibia, and upper humerus, and according to statistics in the United States, there are about 1 in 100,000 new cases each year. Our department accepts 50-70 new patients every year. Treatment: (symptoms + signs + laboratory tests) + imaging + clear diagnosis (puncture or incisional biopsy) Tao Huimin, Department of Orthopedics, Second Hospital of Zhejiang University School of Medicine 2 courses of preoperative neoadjuvant chemotherapy. Surgery: (conventional limb preservation, about 10% amputation) Postoperative, according to the pathology, tumor necrosis rate, the original program continue chemotherapy or change the program chemotherapy for 2 courses. Prognosis: 5-year survival rate of about 70%, local recurrence of 5% or less.