In this paper, the modeling of substrate integrated waveguide (SIW) is revisted based on the finite-difference timedomain method and numerical short-open calibration (SOC) technique. Two error boxes are defined to calibrate the parasitic effects of the impressed electric fields and the errors of finite periodic units. Subsequently, the approximately infinite periodic structure is realized and obtained from a core network of device-under-test. Hence, the complex propagation constant of SIW could be accurately extracted by de-embedding the error boxes. Finally, the numerical examples are presented to verify the accuracy of the extracted parameters.