The conventional FDTD method is extensively applied in dealing with microwave imaging, however, because of the constraint of Courant-Friedrich-Levy (CFL) stability condition, the time-step size required should be smaller enough as well as the fine cells selected is smaller, which brings an increase computational effort. The ADI-FDTD method, on the other hand, utilizing alternating-direction implicit method is available to overcome the constraint of Courant-Friedrich-Levy (CFL) stability condition. It is obvious that the processing result of ADI-FDTD method and conventional FDTD method can coincide with each other perfectly by the MATLAB simulation experiment.