The invention relates to an equalizing device of a battery management system, which comprises a bypass unit, wherein the bypass unit comprises a plurality of bypass devices, at least one part of the bypass devices are energy storage and energy conversion devices, preferably, the energy storage and energy conversion devices can be fans, super capacitors or quadratic chemical power sources, the bypass devices are used in an individual, parallel connection or parallel and series connection way, and the bypass unit also comprises a bypass indicating unit, a switch matrix unit, a battery unit, a data information acquisition unit and a central control unit. The invention also provides an equalizing method of the battery management system; through the invention, the equalizing efficiency is greatly improved under an equal condition, thereby not only shortening the equalizing time, but also satisfying the requirement for automatic and full heat dispersion of a power resistor. The invention enables the heat dispersion and the equalization of the system to be automatically realized without individually providing radiating device, can fully reduce the temperature of an equalizing system, and enables the case and bag design of a battery pack to be simpler and easier to operate and the productionization and the practicalization of a battery system to be further improved.