A redundant power supply system providing rapid start of backup includes at least one primary power supply, at least one secondary power supply and a power integration panel. The secondary power supply includes a voltage regulation and energy saving element which has regulation potential after the secondary power supply being booted up. When the secondary power supply is triggered to shut down and the regulation potential is lower than a low voltage judgment criterion, it enters a standby working mode in which the secondary power supply is restarted for a transient working period to charge the voltage regulation and energy saving element. The power integration panel is electrically connected to the primary power supply and the secondary power supply, and inspects output status of the primary power supply and the secondary power supply in regular conditions to determine to boot up or shut down the secondary power supply.