Abstract: The insulation between the outer skin and core of the signal cable is poor, and thus there are risks of damage to the signal system caused by lightning induced overvoltage flashover. This paper builds the electromagnetic field modeling for the lightning return stroke process, and studies the calculation model of signal cable wires under the excitation of lightning return stroke electromagnetic field. Integrated with the FDTD, a numerical calculation implementation method for the calculation model of signal cable wires in elevated sections is proposed. The induced overvoltage of the cable core is calculated, and the relationship of the magnitude of the induced overvoltage of the signal cable core with the vertical distance from the lightning return channel to the cable, the height of the bridge deck from the ground, and the earth resistivity is obtained. In a typical high-speed railway elevated bridge structure, when the lightning return current is constant, the induced overvoltage amplitude of the cable core decreases non-linearly as the vertical distance from the return channel to the cable grows whereas it increases approximately linearly with the rise of both soil resistivity and the height of the bridge deck from the ground.