The electromagnetic coupling between the control cable with metal shielding sheath and metal conductor of grounding grids in the substation of a power system threatens the safe operation of an electronic system connected with the control cable. In order to simplifying the electromagnetic coupling analysis of this system, the core-sheath model of a control cable is replaced by a parallel multi-conductor model with theoretical analysis and numerical computation in this paper. From analysis of the resistance and the self-inductance of the sheath, the mutual inductance and the capacitance between the core and the sheath in both models, four nonlinear equations to solve the four unknown parameters in the parallel multi-conductors model are established. A program has also been coded to solve the equations. The results of the parallel multi-conductors model are compared with the analyzed ones of the actual control cable by the PSCAD software package. They have good agreement with each other.