In order to improve the reliability of the levitation sensor in maglev train, the mechanism of the surge under the circumstances of thunder strike and power supply interference were analyzed, and the details of the surge experiment were confirmed. In view of current flow capacity, feasibility of the existing circuit design to suppress surge was explained, and the insufficiency of the reliability at high temperature was pointed out. From the analysis in the aspects of voltage reducing and current shunting, the impact of the surge to the sensitive components is reduced by a large-capacity capacitance shunted in front of the original circuit, and the capability of the sensor power to suppress surge is promoted.