For the low efficiency and poor accuracy of the resonant cavity transmission line model based on the double frequencies approximation, this paper proposes a fast algorithm based on Padé approximation and gives the corresponding fast and accurate Spice-compatible resonant cavity transmission line model. Compared with the double frequencies approximation using the single LC resonant circuit, Padé approximation can adjust flexibly and improve the efficiency and accuracy of the model due to using multiple LC resonant circuits. Simulation results ...