In order to balance the capacity of battery cells in charging and discharging process and reduce the loss during equalization process, a charge and discharge equalization strategy for battery packs based on remaining capacity estimation is proposed. Different from traditional equalization strategies based on State Of Charge (SOC) estimation, this strategy uses the remaining capacity of battery cells as equilibrium target. Comparing this strategy with traditional equalization strategy, the calculation results show that under certain premise, the proposed strategy can reduce the total amount of charge transferred during the equilibrium process, thus reducing the loss. The charging and discharging simulations of three serially connected lithium-ion batteries using the proposed equalization strategy and the SOC estimation based equalization strategy have been carried out respectively. The results show that the proposed strategy can not only achieve balance among battery cells at the end of charge and discharge, but also reduce the energy loss. This work is supported by National Natural Science Foundation of China (No. 51707126) and Science and Technology Project of State Grid Corporation of China (No. SGLNDK00DWJS1800020).