Inclusion Criteria:
1. Age ≥ 65 years ;
2. Patients with symptomatic severe aortic valve stenosis (evaluated by echocardiography: transaortic valve pressure gradient ≥40mmHg (1mmHg=0.133kPa), or transaortic valve blood flow rate ≥4m/s, or aortic Valve area\<1.0cm2, or AVA \<0.5cm2 /m2);
3. NYHA ≥ II;
4. Life expectancy\> 12 months;
5. Patients who are anatomically suitable for transcatheter aortic valve implantation;
6. After evaluation by two or more cardiovascular surgeons, patients who are unsuitable for surgery; or patients who refuse surgery after sufficient communication by the surgeons and are at high risk of routine surgery;
7. Patients who can understand the purpose of the trial, voluntarily participate in and signed informed consent form, and are willing to accept relevant examinations and clinical follow-ups.
Exclusion Criteria:
1. Acute myocardial infarction occurred within 1 month before this treatment;
2. Congenital single leaf aortic valve;
3. Any therapeutic cardiac operation (including placement of coronary drug-eluting stents) within 30 days;
4. The patient's heart has been implanted with other artificial heart valves, artificial rings, or severe mitral regurgitation (\>3+);
5. Blood system diseases or abnormalities, including leukopenia (WBC\<3×109/L), acute anemia (HB \<90g/L), thrombocytopenia (PLT\<50×109/L), bleeding constitution and coagulopathy ；
6. Untreated severe coronary artery stenosis that requires revascularization;
7. Patients with hemodynamic or respiratory instability, requiring continuous mechanical heart assistance or mechanical ventilation;
8. Patients who need emergency surgery for any reason;
9. Hypertrophic cardiomyopathy with obstruction;
10. Severe left ventricular dysfunction, left ventricular ejection fraction (LVEF) \<20%;
11. The echocardiogram indicates the presence of a heart mass, thrombus or vegetation;
12. A history of acute peptic ulcer or upper gastrointestinal bleeding within 3 months;
13. Are allergic to cobalt-chromium alloys or contrast agents, and cannot tolerate anticoagulation and antiplatelet therapy;
14. The diameter of the aortic valve annulus \<16mm or \>28mm;
15. In any case, patients who refuse surgical treatment in emergency situations;
16. Cerebrovascular accident occurred within 3 months, not including transient ischemic attack;
17. Severe aortic diseases, including abdominal aortic or thoracic aortic aneurysm, obvious curvature of the aortic arch, atherosclerosis of the aortic arch, narrowing of the abdominal or thoracic aorta, and obvious curvature or extension of the thoracic aorta;
18. The iliac-femoral artery is severely obstructed with calcification, severely tortuous or unable to place the 1418F catheter sheath kit;
19. Active infective endocarditis or other active infections;
20. Aortic valve leaflets calcified plaque close to the coronary ostium;
21. Severe disability Alzheimer's disease and unable to take care of oneself in life;
22. Those who have participated in clinical trials of other drugs or medical devices before entering the group and have not yet reached the time limit of the primary research endpoint;
23. The researcher judged that the patient had poor compliance and could not complete the study as required.
