Switching power supplies are gradually replacing linear power supplies in high-power applications with high efficiency, small size, and high performance. The switching power supplies require large amount of input capacitance to meet load stability. During the startup process of the DC power supply, the voltage across the large input capacitor gradually increases from zero to the input voltage. When power supply starts up, input capacitor is equivalent to a short-circuit resistor, and surge occurs. Common surge suppression methods are as follows: the first method is to place series resistors or thermistors in series; the second method is to place transient suppression diodes or thermistors in parallel; and the third method is active surge suppression. The first and the second method are inefficient and are often used in low-power situations. The third method is used widely. This paper proposes an active digital surge suppression circuit with soft start function. Finally, the effectiveness of the method is verified through experiment.