In order to solve the complex calculation problem of the pin waveguide port impedance parameters, a new pin waveguide analysis method is utilized to establish the equivalent circuit model of single pin waveguide. Using the cascading law, when analyzing the three-pin waveguides, the equivalent circuits of the three single pins are cascaded together to solve the pin waveguide problem from the circuit point of view. The impedance parameters of the pin waveguide ports calculated by HFSS electromagnetic simulation software and by equivalent circuit are compared, and the results are consistent. The correctness of the pin waveguide equivalent circuit and the effectiveness of the pin waveguide analysis method are verified. The goal of simplifying the calculation of the pin waveguide impedance parameters is achieved.