The invention relates to a supercharging device and a supercharging method for low-temperature rocket ground redundancy. The device comprises pilot-operated type two-bit two-way normally closed solenoid valves, a two-bit three-way solenoid valve, manual stop valves and restriction orifices arranged on a low-temperature propellent supercharging gas source gas inlet pipeline; the second pilot-operated type two-bit two-way normally closed solenoid valve and the third pilot-operated type two-bit two-way normally closed solenoid valve are started, and tank pressurization is rapidly conducted by gas which passes through the second restriction orifice and the third restriction orifice. According to the supercharging device for the low-temperature rocket ground redundancy, the single-point problem of a low-temperature propellent rocket ground electric supercharging gas circuit is solved, it is guaranteed that a target requirement of narrow window launching is met, four independent solenoid valves are adopted to achieve a series-parallel connection redundant backup, by means of the restriction orifice with different hole diameters, rapid and high-precision supercharging before launching is guaranteed, and the reliability of the rocket launching is improved.