Abstract: The tapered transmission ridged-waveguide is designed by using a method of Green function based on Chebyshev tapered transmission line. The theoretical design is proven by examples with the numerical method. Transient analysis is solved to design results by microwave studio and the analysis shows that the VSWR is less than 1.1 within 40 percent bandwidth. As an output transform device, it is characterized by its short taper length, excellent matching performance, broad operation bandwidth and low VSWR. This ridged-waveguide has been applied to C-band CFA.