To Evaluate Safety and Effectiveness of Transcatheter Aortic Valve System in Patients With Severe Aortic Stenosis

Inclusion Criteria: 1. Age ≥70 years old; 2. Symptomatic severe aortic stenosis determined by echocardiogram, defined as: mean gradient ≥40 mmHg or peak jet velocity ≥4.0 m/s, or an aortic valve area \<0.8 cm2 or aortic valve area index \<0.5 cm2/m2. 3. NYHA Functional Class ≥II; 4. Life expectancy after aortic valve implantation thought to be \>1 year; 5. Native valvular or peripheral vascular anatomy is appropriate for TAVR; 6. Patient is assessed by at least two cardiothoracic surgeons and recorded as not suitable for surgery; 7. Patient can understand the purpose of the study, voluntarily participates and signs the informed consent form and is willing to accept the relevant examination and clinical follow-up visits. Exclusion Criteria: 1. Anatomy is not appropriate for percutaneous valve implantation. Native valve annulus diameter is not in the scope of application(native TAV diameter ≤21mm, or ≥30mm); 2. Evidence of an acute myocardial infarction within 30 days prior to the study procedure, defined as: Q-wave myocardial infarction, or non-Q-wave myocardial infarction, with CK-MB≥2 ULN/or elevated TN (WHO definition); 3. Any treatment for traumatic cardiac surgery within 30 day prior to the study procedure(except coronary revascularization); 4. Pre-existing prosthetic valve in any position(except severely dysfunctional aortic bioprosthesis), or severe (\>3+) mitral insufficiency, or Gorlin syndrome; 5. Hematological abnormality, defined as: Leukopenia (WBC \<3x10\^9/L), acute anemia (Hb \<90g/L), or thrombocytopenia (platelet count\<50×109/L),history of bleeding diathesis or coagulopathy; 6. Hemodynamic unstable requiring myocardial contractile support or mechanical cardiac assistance; 7. Severe ventricular insufficiency. Left ventricular ejection fraction (LVEF) \<20%; 8. Echocardiographic evidence of intra-cardiac thrombus or vegetation etc.; 9. Active pepticulcer or upper GI bleeding within 3 months prior to the study procedure; 10. Cerebral Vascular Accident (CVA) within 3 months prior to the study procedure, including TIA; 11. A known hypersensitivity or contraindication to aspirin, heparin, ticlopidine or clopidogrel, or sensitivity to contrast media, which cannot be adequately pre-medicated; 12. Patients with infective endocarditis or other active stage of infection; 13. Currently participating in an investigational drug or another device trial.