The invention relates to an active equalization circuit of a lithium ion power battery pack. The active equalization circuit comprises the lithium ion power battery pack, a voltage collecting module,a gating circuit, a reversing circuit, an equalizing transformer and an auxiliary battery circuit, wherein the input end of the voltage collecting module is respectively connected with the lithium ionpower battery pack and the auxiliary battery circuit; the output end of the voltage collecting module is connected with a control unit of a battery management system; one end of the gating circuit isconnected with the lithium ion power battery pack, and the other end of the gating circuit is sequentially connected with the reversing circuit, the equalizing transformer and the auxiliary battery circuit; the auxiliary battery circuit comprises an auxiliary single cell, and the equalizing transformer is a multi-winding transformer. Compared with the prior art, the active equalization circuit has the advantages that the structure is simple, the cost is low, the safety and reliability are realized, the capacity of the battery pack is increased, the charge and discharge states of the battery pack can be effectively managed, and the service life of the battery pack is prolonged.