In order to control the grounding current，transient overvoltage and displacement voltage，the neutral grounding device is needed in hydropower station． The fault current in grounding point，the reactance and impedance proportion in fault current，the amplification factor of displacement voltage of neutral point between grounding devices with high impedance and shunt reactance in a hydropower station are compared． The calculations are as follows: in this case，the high impedance scheme can reduce the fault current at the low displacement voltage，but it increases the displacement voltage too，and the adjustment is unidirectional，while the adjustment of shunt reactance scheme is bidirectional，which has better flexibility in the site adjustment．