The invention discloses an energy saving system of an elevator. In the system, a super capacitor group is utilized as a regenerative braking energy storage device of an elevator sub-system and a power supply source for operating the elevator sub-system, energy is stored in the braking process of operating the elevator sub-system, a power source switching control circuit is controlled by a system controller to realize the switching between the super capacitor group and an external alternating current network for supplying the electricity to the elevator sub-system so as to achieve the purpose of saving energy. The system fully utilizes the characteristics of heavy current discharge of a super capacitor, lowers the requirements on the level of the external alternating current network and can synchronously satisfy a peak value power generated when the elevator sub-system is operated, and the super capacitor presents the advantages of long service life, short charging and discharging time, large capacitance density and the like. The system saves energy and synchronously improves the safety of the elevator operation and has very high social benefit and economic benefit.