Objective To investigate the effectiveness of tissue flap grafting and sequential bone lengthening for repairing severe soft tissue and bone defects of the lower extremity after burn injury. Methods Between January 2010 and December 2015, 11 cases of large segmental bone and soft tissue defects in the leg were treated. There were 10 males and 1 female, with a mean age of 28 years (range, 19-37 years). The causes included traffic accident in 8 cases, high voltage electric burn in 2 cases, CO poisoning burn in 1 case. The time from injury to admission was 3-14 days (mean, 6.5 days). The bone defect length was 8-18 cm (mean,14 cm); the skin soft tissue defect ranged from 13 cm × 8 cm to 25 cm × 19 cm. After complete removal of necrotic tissue and lesions of the femur or the tibia, the tissue flaps were used to repair soft tissue defect of the lower extremity in one-stage operation; bone defect was treated by Orthofix single side external fixation or Ilizarov ring external fixation in two-stage operation. Results Eleven flaps survived completely, primary healing of incision was obtained in the others except for 1 patient who had necrotic bone infection, which was cured after removing necrosed femoral bone and filling with antibiotic bone cement spacer. During bone lengthening, pin tract infection occurred in 1 patient, and infection was controlled after dressing change. Bone lengthening ranged from 8 to 18 cm, with an average of 14 cm. After prolonged extension, the external fixator was retained for 4-12 months (mean, 6.5 months). All bone defects were repaired with bone healing time of 12-22 months (mean, 17 months). All patients were followed up 8-24 months (mean, 15 months). No vascular and neurological complication occurred during operation; no osteomyelitis or re-fracture occurred after operation, and the recovery of the lower extremity function was good. Conclusion Tissue flap grafting combined with bone lengthening is an effective method to repair severe bone and soft tissue defects of lower extremity.