Currently, the optimal antithrombotic therapy after transcatheter aortic valve replacement (TAVR) remains still unknown., The purpose of the study is to compare aspirin versus clopidogrel monoantiplatelet therapy for preventive effect on leaflet thrombosis in patients undergoing TAVR for severe aortic stenosis. This study is designed as a prospective, multicenter, open label, randomized controlled study. Eligible patients will be randomized to aspirin or clopidogrel monotherapy after TAVR. Patients will have dual antiplatelet therapy of aspirin 100 mg and clopidogrel 75 mg for 4 weeks after TAVR and then subsequent monoantiplatelet therapy of either aspirin 100 mg or clopidogrel 75 mg according to the randomization. Leaflet thrombosis will be assessed with cardiac computed tomography (CT) and transthoracic echocardiography at 3 months after TAVR. Patients will be clinically followed for 6 months. The primary endpoint is the Incidence of leaflet thrombosis on cardiac CT at 3 months.