In order to meet the performance of PEV demand, the car's energy was provided by series of power batteries. With the wide application of PEV, the consistency problem of on-board dynamic battery has become more and more attention by people. As the existence of consistency problem, available capacity and service life of battery pack are much less than that single fuel cell.Therefore, the balance management of the battery pack has important practical significance of using a group of cells. This paper mainly research on the equalization technique of power Li-ion battery pack.