The clinical use indications for transcatheter aortic valve replacement (TAVR) for the treatment of severe symptomatic aortic stenosis (AS) have expanded from patients at high surgical risk to those at low risk based on the results of multiple large-scale randomized trials. However, patients with bicuspid AS have traditionally been excluded from clinical trials due to their unfavorable morphological characteristics. Bicuspid aortic valve (BAV) is the most frequent congenital heart disease, occurring in 1% to 2% of the total population and affects more than 20% of octogenarians undergoing isolated aortic valve replacement for AS. In recent years, TAVR in patients with bicuspid AS has been the focus of research, especially with respect to the standard of prosthesis size selection. Annulus-based prosthesis size selection using computed tomography (CT) is the standard sizing strategy for tricuspid AS, but no standard sizing for bicuspid AS has been developed thus far. According to Western TAVR experiences, transcatheter heart valve (THV) size selection for BAV patients should be based on the annular structure assessment by CT measurement, whereas Chinese experiences favor adopting the supra-annulus structure assessment for THV size selection. This article will review annular and supra-annular sizing for prosthesis size selection in patients with bicuspid AS before TAVR and discuss which has more favorable clinical outcomes.