The invention provides a power frequency follow current testing device and an application method thereof; the testing device comprises the following units: a power transformer used for converting a power grid voltage into a power frequency voltage, wherein the power transformer winding inter-turn insulating material employs yellow varnished silk, and the inter-layer insulating material employs fiberglass cladding flat wire; an impact voltage generator with the charging capacitor electric capacity as 0.05 [mu]F, a wave front resistor resistance as 80 [omega] and a wave tail resistor resistance as 2100 [omega]; the impact voltage generator is connected in series with an impact side protection circuit, and then the output end is connected in parallel with a tested product; the power transformer and a power frequency side protection circuit are connected in parallel, and then the output end is connected in parallel with the tested product; the testing device also comprises a control measuring circuit used for determining whether to trigger to form an impact voltage or not according to the power frequency power phase. The testing device can better simulate the lightning wave conditions happening in network operations, can bear higher overvoltage and overcurrent, thus ensuring high reliability, and using fewer protection circuits.