The conducted EMI simulation plays an important part in the SMPS in the product design. The analysis of common mode noise is much more complex than differential mode noise. The CE simulation accuracy depends on the accuracy of CM mode noise. CM noises are determined by the electric coupling between the voltage jump point and the ground. Traditional the CM models of the electric coupling between the primary and secondary windings of the transformer and between the magnetic components and the ground is got by tested with two-port equipment what are inconvenient for EMI simulation. In this paper the method by using FEA simulation method to get the electric coupling between the primary and secondary windings and the electric coupling between the magnetic components and the ground without test was proposed. Finally, the consistency between the experiment results and simulation results verify the proposed method to be correct and feasible. It provides a new idea for the modeling of the electric coupling for magnetic components.