Transient electromagnetic pulses can be coupled to vehicle electronic system through cables, causing electronic equipment disturbance, even damage. Research on the suppression characteristics of transient protection devices on electromagnetic pulse can provide strong support for vehicle electromagnetic hardening. In this paper, we build the electromagnetic simulation model of vehicle engine by considering the key metal structure, cables and electronic equipment. Cables coupling characteristics were calculated under transient electromagnetic pulse; A test platform for transient protection devices was built, and the response characteristics of transient voltage suppress (TVS) and metal oxide varistor (MOV) were obtained, such as response time, clamping voltage, and peak voltage leakage. Based on the simulation and test results, a type of TVS was selected. This TVS is used to the signal line electromagnetic protection of camshaft position sensor. The result shows that this type of TVS has an ability of cable interference suppression close to 20 dB, and placing it in the front of filter can effectively suppress cable coupling interference and protect terminal equipment.