The DC synthetic load is connected to the DC distribution network, which will affect the stability of the system. In order to reduce the impact of load on DC system, in this paper, a method to optimize the synthetic load of DC distribution network by using ESS is proposed. First, based on the synthetic load characteristics, the power coordination relationship between the load and the ESS is studied to improve the load characteristics. Second, while improving the load characteristics, the ESS is optimally configured with the objective of minimum ESS investment cost. Finally, a case study shows that the proposed method in this paper can effectively improve the load characteristics, reduce the DC voltage fluctuations, and improve the stability of the DC distribution network.