Background: In recent years, the composite anterolateral thigh free flap with tensor fasciae latae or vastus lateralis has been a new-applied type of flap that can provide very good reconstruction materials in complex defects of lower leg and foot. The study purpose is to evaluate the systematically complications of donor site, related factors to results of the donor area, in order to apply the result to improve the treatment, which have not been much reported in literature. Materials and Methods: Systematic donor site morbilidy evaluation in a prospective, uncontrolled clinical descriptive study of 33 composite anterolateral thigh free flaps in various forms to reconstruct anatomical structures or to resconstruct deep defects combined with covering the surfaces for complex soft tissue defects in lower extremities for 32 patients due to different causes in lower leg and foot area from 2014-2019 at Hue University of Medicine and Pharmacy. Examining and evaluating aesthetic and functional result of donor-site 3 months and 6 months up to 2 year after surgery; evaluating the correlation between the width and the type of the flaps and donor site closure methods. Result: In 33 composite flaps used, flap width to thigh circumference less than 20% in 27 cases (81.8%), more than 20% in 6 cases (18.20% ); There were 28 cases in which the donor site was directly closed, 5 cases required skin graft; All direct closed cases had flap width/ thigh circumference index below 20%; On the contrary, in cases having this index greater than 20%, the donor site required skin graft with p < 0.01. There are 11/33 (33.33%) of cases reported complications in donor site ; lateral thigh paresthesia is the most complicated complication with 8/33 cases (24.24%), followed by bad scarring 3/33 cases (9.09%). Conclusion: Long term follow up donor site morbility after composite anterior thigh free flap present 11/33 cases (33.33%): mostly complications of the donor site are thigh paresthesia with 8/33 cases (24.24%), and bad scarring 3/33 cases (9,09%), which improve time by time. Keywords: Composite anterior thigh free flap, lower extremities soft tissue defect, donor site morbidity