Objective:To explore the method and curative effect evaluation of repairing and rebuilding the long segmental bone defect after resection of long bone malignant tumors in adolescents.Methods:Reviewed our experience in 10 patients. Among them, 4 were male and 6 were female. The age was 10.2 years old (range, 6-16 years old). Including 7 cases of osteosarcoma, 3 cases of Ewing's sarcoma; 2 cases of humerus tumors, 7 cases of femoral tumors, and 1 case of tibial tumors-who presented between April 2015 and October 2019, in which the proportion of bone defect account for 71.4%-89.3% of the total length of diseased bone after tumor resection, with an average value of 80.9%. Considering the epiphyseal growth of young people, on the premise of ensuring enlarged tumor resection, we use traditional fibula autograft and prosthesis combined with steel plate, 3D printing design to retain the super-prosthesis of the epiphysis, and 3D printing bone trabecular was processed for the sake of making it grow successfully into the binding part of prosthesis and bone as we expect, simultaneously, the design of the short-force arm retaining the bilateral epiphysis can assit the steel plate and interlocking screws to enhance the stability.Results:The operation was completed successfully, and there were no complications such as nerve and blood vessel injury during the operation. After follow-up of 4-8 months, with an average follow-up of 22.9 months. One patient's review of X-ray film after 2 years of the operation showed that the transplanted fibula had a sign of bone resorption, and the internal fixation was in it's original position without obvious abnormalities. Two cases' auxiliary steel plates had fractured within one and a half to two years after surgery. With replacing the fractured steel plates, the internal fixation was good until now. According to the evaluation standards of the International Society of Limb Salvation: 2 cases of humerus osteosarcoma were respectively scored 23 points, 26 points, an average of 24.5 points; 4 cases of femoral osteosarcoma and 3 cases of femoral Ewing's sarcoma respectively scored 26 points and 25 points, 19 points, 30 points, 27 points, 24 points, 28 points (average, 25.6 points); 1 case of tibial osteosarcoma scored 26 points; all obtained relative satisfying treatment results.Conclusion:The combination of 3D printing and traditional machining techniques to produce an individualized long segmental prosthesis that preserves the epiphysis which applicated in the limb salvage treatment of bone malignant tumors can achieve excellent therapeutic effect.