Method and system for supplying power to primary loop of nuclear power plant during hydrostatic test

A method and system for supplying power to a primary loop of a nuclear power plant during hydrostatic test are provided. The method comprises, a first step S1 of successively powering and starting a main pump on at least one incoming line using an auxiliary power supply and further carrying out a load limiting on the same incoming line as the main pump. A second step S2 of powering and starting a charging pump on the at least one incoming line by the auxiliary power supply. A third Step S3 of powering and starting a hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure. Finally, a fourth step S4 of automatically starting an emergency power supply on one of the at least one incoming lines to power a load if the auxiliary power supply fails in any of the above powering steps. By applying the present method no main power supply is needed to be available, and high safety and reliability are ensured.