The high-altitude electromagnetic pulse (HEMP) generated by a nuclear explosion in the outer atmosphere poses the most serious threat among all electromagnetic pulses due to its wide coverage (radius in thousands of kilometers), high attack intensity, and multiple destructive targets. However, there is currently no real experimental research on the impact of HEMP on the power grid, and the law of the impact of HEMP on the power grid is still in the early stage of research. This article will conduct a true type test on the HEMP response characteristics of lightning protection equipment in the power grid. Based on the response time of lightning arresters to lightning currents, this study experimentally investigates the response characteristics of lightning arresters when HEMP induce instantaneous high currents in wires. Based on the experimental results, the effectiveness of existing lightning arresters in responding to electromagnetic pulses is analyzed, and improvement suggestions for the response time of lightning arresters to HEMP are proposed.