A hierarchical equalization circuit is proposed to solve the problem of partial over charge and over discharge of lithium-ion battery, due to the inconsistency of single battery in series group. The hierarchical equalization circuit takes the state of charge (SOC) value of single battery as equalization variable, divides battery pack into three groups, and carries out equalization based on Buck converter within the group; Buck-Boost circuit was built between each group to realize bidirectional flow of electricity between groups and balance between groups. The combination of intra-group balancing and inter-group balancing improves the balancing efficiency. The simulation results built on MATLAB/ Simulink platform show that compared with the equalization circuit based on Buck converter and Buck-Boost converter, the hierarchical equalization circuit can operate under static, charging and discharging conditions, compared with Buck-based equalization circuits, the equalization time is reduced by 21%, 18% and 30%, respectively, and compared with Buck-Boost equalization circuits, the equalization time is reduced by 17%, 29% and 15%, respectively. The equalization experiment of the battery pack shows that the circuit can improve the consistency of these single batteries, control the SOC value range of the battery pack within 0. 1%, solve the problem of overcharge and over discharge of partial batteries, and improve the equalization efficiency.