Controlled Source Radio Frequency Geomagnetic Method (CSRMT) is an active source electrical exploration method based on geomagnetic (MT) technology in geophysical science. A movable artificial excitation source is built to detect the changes of underground electric and magnetic fields and calculate the electrical properties of underground structures. The construction of a stable excitation system is an important part of the CSRMT design, but the inverter circuit composed of power devices will produce high voltage overshoot during the turn-on and turn-off process, which not only affects the waveform quality but also leads to the damage of the circuit devices due to exceeding the voltage withstand level, therefore, setting up buffer circuits is an effective way to mitigate the voltage overshoot to ensure the normal operation of the circuit. First of all, the causes of voltage overshoot in the switching process are analyzed by taking MOSFET as an example, selecting a discharge-blocking RCD buffer circuit and analyzing the working principle. Through simulation and experiment, it is shown that the discharge-blocking RCD buffer circuits have strong voltage overshoot mitigation and suppression ability, low loss, and can be used in high-frequency inverter circuit excitation system.