Abstract: In order to test lightning protection effect of protection gap for 35 kV power line, the paper simulated lightning invasion in 35 kV transformer taking 35 kV overhead line of a mine as model by use of ATP-EMPT electromagnetic transient analysis software, and compared over-voltage peak value at high-voltage side of transformer before and after installing the protection gap. The compare result showed that the protection gap can significantly reduce the peak value of lightning invasion wave at high-voltage side of the transformer after 35 kV power line is subjected to single-phase or three-phase lightning. The paper also analyzed lightning withstanding level and rate of lightning trip of 35 kV power line with lightning protection gap, whose conclusions are the lightning withstanding level reduces and rate of lightning trip rises, while the two parameters satisfy requirements of DL/T 620-1997. The application results showed that the lightning protection gap installed on 35 kV line of coal mine can effectively inhibit lightning from invading substation device, but should run with automatic reclosing device for higher reliability of line lightning protection.