When the wiring harness operates in a high-temperature environment, it is essential to start with material quality control. Conductors should preferably be made of nickel-plated or silver-plated copper alloy, or nickel-based alloy if necessary, to suppress the surge in contact resistance caused by the thickening of the oxide layer. For the insulation layer, priority should be given to PTFE, polyimide, or silicone rubber, which can maintain dielectric strength and flexibility at temperatures above 200℃, preventing cracking and electrical leakage due to thermal aging. The sheath layer is recommended to use fluororubber or silicone rubber, combined with stainless steel wire braiding, which can both block thermal radiation and resist mechanical wear. During the wiring stage, it is necessary to avoid heat sources such as exhaust pipes and turbochargers. If avoidance is not possible, aluminum foil heat-insulating corrugated tubes or ceramic fiber sleeves should be added, and high-temperature resistant silicone rubber pads should be placed at the fixed buckle to prevent plastic cable ties from being directly heated and breaking. A thermal expansion arc should be reserved in the transition section between the high-temperature range and the normal temperature range to prevent the wires from being pulled thin or breaking during repeated thermal cycles. The connector selection must meet the temperature rating of -40℃ to 150℃ or higher, and the tail outgoing line should maintain a straight section. Forced bending is prohibited to avoid local crumpling of the insulation and the formation of electrical tree channels. After the overall debugging, a 1000-hour constant temperature aging test, a thermal shock cycle of -40℃↔200℃, and a damp heat verification test at 85℃/85%RH should be conducted. Through local discharge and voltage withstand retesting, it is necessary to confirm that the insulation is free of micropores and carbonization traces before it can be put into long-term operation. Only by integrating materials, structure, process, and verification can the high-temperature failure rate be minimized.