Different strategies exist in the treatment of chronic long occlusion of the superficial femoral artery. Traditionally, these patients should be treated with bypass. If the great saphenous vein is unavailable, doctor has to choose artificial vessel as graft. Now, the skill of endovascular treatment is developing rapidly, and lots of doctors think most of such patients could be treated with stent. The purpose of this trial is to compare stent and artificial blood vessel bypass in the treatment of long occlusion of the superficial femoral artery. The study hypothesis is that patency rates are comparable and therefore the minimal invasive treatment of stent can be considered in such patients.