The invention discloses an RC serial connection-based very fast transient overvoltage suppression method. A to-be-controlled circuit is subjected to simulation to determine circuit peak values in a transformer, an isolation switch and a bus when a circuit transformer end, an isolation switch end and a transformer side isolation switch end are connected with a series RC branch respectively; a suppression circuit connecting position is selected according to suppression requirement; and in the chosen position, simulation of the suppression effects of the RC series branch with different values is performed so as to determine the optimal suppression effect range to be used as the capacitance value and the resistance of the RC. By virtue of the suppression method, it is ensured that the peak value of the VFTO (very fast transient overvoltage) can be effectively lowered, and compared with the conventional parallel RC branch suppression method, the suppression method disclosed in the invention is lower in power consumption; and the effectiveness of the method is verified through simulation.