Abstract: The infinite impulse response (IIR) filter with the partial fraction expansion form is employed to model the transfer impedance and transfer admittance of the shielded cable. The models are then incorporated into finite-difference time-domain(FDTD) scheme to analyze the coupling of the shielded cable. The numerical results prove that the proposed method can provide more precise models of the transfer impedance and transfer admittance, and can be easily combined with FDTD algorithm as well. Compared with the traditional methods， the present one can obtain more accurate response of the inner conductor.