Abstract: Comparative study of the multi-mode theory with the Computer Simulation Technolgy(CST) software is carried out for the numerical simulations of a new coaxial Bragg reflector corrugated with sinusoidal ripples.Results show good agreement between the multi-mode theory and the CST software.However,compared with the CST software,the multi-mode theory has the peculiarities of easy programming,fast calculation speed,and convenient adjusting,and the bandwidth of the coaxial Bragg reflector with positive taper can be narrowed by increasing the tapering angle,whereas the bandwidth of the coaxial Bragg reflector with negative taper can be expanded by increasing the tapering angle.The residual side-lobes of the frequency response can be effectively suppressed by employing the windowing-function technique.These characteristics of a tapered coaxial Bragg structure are favorable to improvement of the performance as a reflector or a filter in its applications.