Abstract: The alternating direction implicit finite-difference time-domain (ADI-FDTD) method has been proposed toovercome stability limitations in conventional FDTD methods. Despite its high efficiency, the ADI-FDTD method sufferssignificant errors at large time steps. The ER(error reduced)-ADI-FDTD method increases accuracy without muchcomputation addition, by compensating truncation errors, but only two dimensional and non-dispersive cases are considered. In this paper, an error reduced ADI-FDTD method for Debye dispersive media is proposed based the original ER-ADI-FDTD,complete three dimensional equations are derived. Calculation results are checked and compared with existing methods.