It is found that the reflection error of Mur’s first-order absorbing boundary condition can be cancelled effectively by applying the ABC twice to an electromagnetic field on two diagonally neighboring nodes on the x-t

y-t and z-t planes

according to which a twofold Mur’s first-order ABC（TMFABC） is developed. It is very convenient to apply TMFABC to multilayer structures. The absorption efficiency of TMFABC is obviously better than that of Mur’s first-order ABC and its super algorithm

especially at lower frequencies. A FDTD software using TMFABC has been written to extract the circuit model parameters of transmission lines in high-speed integrated circuits.