Objective:To investigate the causes of groin lymphatic fistula after transluminal ultrasonic angioplasty (TUA) in the treatment of deep vein thrombosis(DVT) of lower extremity through groin incision. Methods: A retrospective analysis of the causes of groin lymphatic fistula(GLF) in 72 patients with DVT after treatment of ultrasonic ablation was made. Results:TUA and thrombectomy using Forgaty balloon catheter for DVT of lower extremity achieved successful recanalization in all the 72 cases (100%). Of the 72 cases,51 had iliac vein stenosis,the venous stenosis disappeared after balloon dilation;among the 51 cases,6 cases received stent placement. GLF occurred postoperatively in 60 cases. No death occurred in this series. Conclusions:TUA is an effective method in the treatment of DVT of lower extremity,but the incidence of postoperative GLF is high.The causes of GLF may be related to the injury of lymphatic vessels, increase of quantity of lymph flow induced by increased venous pressure, infection, surgical technique factors and postoperative medicine therapy etc.