Because plug-in hybrid electric vehicle (PHEV) batteries can obtain relatively cheap power through the grid, the traditional control strategy only considers the full use of battery power, but ignores the excessive use of battery, which will accelerate the decline of power battery capacity. Therefore, how to make full use of battery power and control the decline of battery capacity is a new research focus. Based on the semi-empirical decay model of battery, the energy management strategy of balancing the degradation of battery capacity was established by introducing the factor of battery utilization degree. The multi-objective optimization problem was transformed into a single objective problem by selecting the appropriate weight factor through Pareto non-inferior target domain. The dynamic programming algorithm was used to obtain the global optimal solution of weight coefficient. The optimal weight coefficient was selected by weighing the fuel consumption and battery capacity decline degree under different weights. In the case of equivalent fuel consumption, when the weight coefficient is 0.9, the decay rate of battery life can be effectively inhibited. Finally, the validity of ECMS strategy is verified by comparing it with the dynamic programming solution under the same weight.