The trial includes two parts and here is part I. This part is a multi-center, prospective, randomized, controlled study to compare the therapeutic effect of stent and bypass to chronic long occlusion of the superficial femoral artery in DM patients. Totally 70 patients will be entered into the study. The lesion of the femoral artery should be TASC B、C or D and the patients should suffered ischemic symptom with Rutherford 3-6.The lesion does not extend beyond the aortoiliac artery or blow-knee popliteal artery, with at least 1 vessel infra-popliteal runoff to the foot.