A Study of Below The Knee Arteries' Stenosis or Occlusion Treated With LEGFLOW OTW

Inclusion Criteria: * age from 18 to 85 years (include 18 and 85 year); * critical limb ischemia subjects (Rutherford classification from 3 to 6) * expective survival more than 1 year; * can understand the study objective, self willing enrolls and sign the informed consent, and accept scheduled followed up at the specific time. Angiographic inclusive criteria: * reference vessel diameter 2.0-3.5mm; * stenosis or occlusion in arterial vasculature below the knee shall have distal outflow; * target lesion stenosis ≥70% or occlusion, length ≤270mm; * if subject has ipsilateral / contralateral iliac lesions, the iliac lesion shall meet all the following criteria: * iliac lesion or occlusion length ≤100mm and * shall be treated earlier than the target lesion and * shall be treated successfully. the successful treatment standard: 1) residual stenosis \<30%; 2) without flow limiting dissection 3) without thrombosis, embolism or any other serious adverse events Exclusion Criteria: * subjects currently participate in other drugs or medical devices clinical study and have not reach the primary endpoint; * childbearing aged women whose pregnancy test before intervention operation is not negative, and lactating mothers; * subjects with renal function insufficiency (serum creatinine\> 2.5mg / dL or in renal dialysis); * subjects have known be allergy or contraindication to the contrast agent, paclitaxel, heparin, antiplatelet, anticoagulant or thrombolytic agents; * subjects plan to a major amputation (over metatarsal level); * stroke subjects within 3 months or stroke subjects with severe hemiplegia and aphasia associated sequelaes over 3 months before the intervention operation; * subjects with acute myocardial infarction, thrombolytic therapy or angina within 30 days before the intervention operation; * subjects whose target lesion limb have gangrene (the gangrene range over the metatarsophalangeal joint); * target lesion is a stenosis or occlusion that have prior been treated by scaffold implantation, DEB, ordinary balloon catheter or bypass graft; * lesions and /or occlusion locate or extend to popliteal artery or below ankle joint; * subjects requiring be intervention in bilateral lower limb; * the stenosis lesion of ipsilateral femoral artery or ipsilateral popliteal artery have a diameter stenosis ≥50% untreated before the intervention operation; * ipsilateral femoral artery or ipsilateral popliteal artery has single or adjacent lesion length ≥15cm, or ipsilateral femoral artery or ipsilateral popliteal artery has multiple lesion and one of these multiple lesion length ≥10cm or occlusion; * \- adjacent lesion: 1) interval no more than 30 mm, 2) can be treated as a single lesion; * \- multiple lesion: 1) interval no more than 30 mm, 2) need to be treated as multiple lesion; * the residual stenosis still ≥30%, even when the length \<15cm and stenosis ≥50% single or adjacent lesion in ipsilateral femoral artery or ipsilateral popliteal artery has been treated, or when each lesion length \<10cm and stenosis ≥50% multiple lesion in ipsilateral femoral artery or ipsilateral popliteal artery has been treated; * DES and /or DEB has been used in the inflow vessel of lesions treatment; * subject has no patency vessel below the ankle artery before the intervention operation; * target vessel aneurysm; * acute or subacute thrombosis in target vessel; * angiography shows severe calcification in the target lesion (before contrast injection or digital subtraction angiography, intensive annular calcifications that make target lesion not expansion and / or a calcification within the target lesion and locate on either sides of the vessel wall whose continuous length over than 5cm); * lesions that the guild wire cannot pass through; * subjects need be treated by thrombus endarterectomy, percutaneous transluminal plaque circumcision or laser treatment device indicate by intraoperative angiography;