The invention belongs to the field of new energy vehicles and battery management systems, and particularly relates to an equalization structure for a vehicle-mounted composite power supply system andan equalization method of the equalization structure. The equalization structure comprises a power lithium battery module, a super capacitor module, a bidirectional high-low-voltage DC / DC converter, alithium battery switch matrix, a super capacitor switch matrix and an equalization controller. Disequilibrium of energy consumption of a power battery is achieved by means of the composite power supply system, so that the running effect of a power system is improved. A battery equalization control system collects working condition parameters of the composite power supply system in real time and makes a decision equalization scheme, a lithium battery and the super capacitor switch matrix control the starting and shutting of equalization, and the energy in the power battery is transferred intoa super capacitor through the high-low-voltage DC / DC converter. The balance control system realizes the dynamic and static balance of the power battery, improves the performance and efficiency of thepower battery, prolongs the service life of the power battery, improves the problem of thermal management in a equalization circuit, improves the follow-up routine of an electric vehicle and realizesthe real-time correction of an SOC value of the power battery.