The E1 phase of the high-altitude electromagnetic pulse （HEMP） has a high field strength, a fast rise time, and a short duration. It will damage the end of the intelligent equipment through the substation internal control cable coupling. Therefore, it is of particular importance to analyze the HEMP coupling response characteristics of the substation internal control cable. Through conducting research on the actual cable conditions of typical substations, the end coupling response level of switching and analog transmission cables in a substation under HEMP environment are simulated and investigated. The study reveals that when the shield is not grounded, the end of the cable induces a high voltage of approximately 70 kV. Additionally, when the core wire is grounded, the short-circuit current is approximately 4 A. The amplitude of the shield's grounding current is approximately 60 A. Finally, a biconical-linear-grid antenna is constructed as a horizontally polarised HEMP simulator. The control cable is tested in the field and compared with the simulation results to verify the validity of the simulation method.