Abstract: Objective To explore the clinical effect of free anterolateral thigh flap in repairing large annular soft tissue defect of lower leg after burn. Methods From January 2014 to December 2018, 9 patients with large annular soft tissue defects of lower legs after burns were hospitalized in Zhengzhou First People′s Hospital, including 1 case with wounds on both legs. After debridement, area of wounds was 16 cm×11 cm-38 cm×21 cm, and the burn wounds were repaired with free anterolateral thigh flaps in the area of 18 cm×12 cm-32 cm×24 cm. End-to-end anastomosis of posterior tibial vessels or anterior tibial vessels with lateral circumflex femoral vessels was performed in manual way or by microvascular stapler. For the affected legs without condition for anastomosis, the sound medial lower leg flaps with areas of 10 cm×8 cm-15 cm×10 cm were excised and made into skin tubes, the posterior tibial vessels of the flaps were anastomosed with the vessels of free anterolateral femoral flaps, and the wounds of the injured lower legs were repaired by bridge-type cross-over free transplantation of anterolateral thigh flaps. The pedicles were broken 4 to 5 weeks later. The donor site was transplanted with autologous intermediate split-thickness skin graft from thigh. The outcome of the treatment, the number of perforators included in the flaps, and the anastomotic vessel in the recipient area of patients were recorded. The anastomosis time between manual way and microvascular staplers was recorded and compared. The patency of blood vessels, methods of free transplantation, and follow-up condition were recorded. Data were processed with Wilcoxon rank sum test for two independent samples. Results All the 10 free flaps and skin grafts of 9 patients survived, and all the wounds were closed by primary operation. Seven flaps contained two perforators each, and three flaps contained three perforators each. The anastomotic vessels were posterior tibial vessels in 6 recipient areas and anterior tibial vessels in 4 recipient areas. Microvascular stapler was used to anastomose 12 veins, while 8 veins and 10 arteries were anstomosed manually. The time consumed by the former method was 4.00 (3.55, 4.38) min, significantly shorter than 12.80 (12.13, 13.40) min of the latter (W=78.00, P<0.01). The patency rates of veins and arteries were 100%. There was no vascular crisis due to vascular anastomosis. Three patients underwent bridge-type cross-over free transplantation, while the others underwent conventional free transplantation. Follow-up for 3 to 30 months showed that the donor site of the thigh had good motor function, without numbness or pain, but hypertrophy of scar could be seen. Four patients had slightly overstaffed flaps transplanted in the recipient area of the lower legs, while the other patients were satisfied with their appearance, and the walking function of the affected limbs gradually recovered. Conclusions Free anterolateral thigh flap transplantation is a safe and reliable clinical limb salvage method for the repair of large annular soft tissue defect of lower leg after burn. Intraoperative application of microvascular stapler for venous anastomosis can shorten the time of vascular anastomosis and has great clinical application value.