Coaxial-waveguide transition plays an important role in microwave system. Based on the influence of waveguide ladder exerted on transmission performance of electromagnetic wave in guided wave system, this paper demonstrates the situations of this structure applied in Ku band coaxial-waveguide converter designation. The reflected wave and insertion loss have been reduced by using a multi-steps structure with the coaxial probe excitation. The effectiveness of impedance matching is well-improved, and the transmission performance of coaxial-waveguide converter is highly-advanced. Simulation results proved the effectiveness of waveguide ladder in designing coaxial-waveguide converters. The VSWR of coaxial-waveguide transition designed in this paper is less than 1.04 in the 12.4–18 GHz octave bandwidth, and the high modulus produced is very small.