Abstract: The transient response can be generated by the interaction of nuclear explosion rays with materials in systems which include the X-ray direct responses on wires and cables. The circuit model which was used for the X-ray direct responses research and engineering prediction was proposed. In the model, the electrons movement trail and responses mechanisms were considered. Current source and capacitance definition and its expressions in the circuit model were introduced. As an example, center conductor voltages of the load under the condition of matching load of cable ends were calculated using the circuit model for X-ray with energy of 300 keV. The numerical results indicate that the capacitance is the key parameter for the circuit model, and the electron attenuation coefficient is appropriate for the electrons range and capacitance calculation.