A standby-power-supply rapid switching system based on a super capacitor comprises a main power supply and a standby power supply of a power grid and is provided with a transition power supply, a bidirectional converter and a solid-state change over switch. Output of the transition power supply is connected to the solid-state change over switch via the bidirectional converter. The transition power supply adopts the super capacitor. The solid-state change over switch comprises an antiparallel thyristor valve and a composite structure which is connected in parallel with a rapid mechanical switch. Outputs of the main power supply, the standby power supply and the transition power supply are connected in parallel and then are sent to the solid-state change over switch. After being selected via the solid-state change over switch, the outputs provide power for a sensitive load. During normal operation, the main power supply provides power; after the main power supply has a fault, the power is switched to the transition power supply through the solid-state change over switch; and after an output voltage of the standby power supply satisfies a requirement, the power is switched to the standby power supply through the solid-state change over switch. Applicability of the scheme in the invention is wide and the scheme is especially suitable for a condition that a distribution network takes a diesel generator as the standby power supply. Electric energy quality can be improved, power supply reliability and continuity are increased.