According to the requirements of GJB 181A and GJB 181B-2012, airborne equipment using a 28 V power supply system must maintain normal operation under a 50 V/50 ms voltage surge. The typical operating range of DC/DC converters in airborne equipment is 9–36 V or 16–40 V. To ensure safe operation and prevent damage during a 50 V/50 ms surge, the clamping characteristic of a MOSFET's gate-source turn-on voltage is typically utilized to clamp the input voltage within the safe operating range. A voltage surge can be regarded as a step excitation to the MOSFET. Due to the influence of parasitic parameters, the MOSFET's output may oscillate, leading to abnormal operation of the airborne equipment. This paper analyzes the impact of MOSFET parasitic parameters on surge suppression effectiveness and proposes a solution based on the analysis. The solution has been verified as simple, effective, low-cost, and highly practical.