In the early research work,the concept of building energy smart grid based on natural gas based distributed energy system is proposed. For design of energy storage system applied to NDES-SG, basic principles of system design are given which follows energy saving and efficiency increasing in this paper. To interpret integration, energy saving potential and system evaluation method of NDES-SG, Combining with design principles of energy storage system, a simplified typical case system is presented. The influence of energy storage system design on the NDES-SG performance is studied taking ice thermo storage system as an example and system energy saving rate for evaluation criteria. The results show that NDES-SG with a reasonable storage system design can realize energy saving rate approximately 30% compared with NDES-SG without energy storage system. NDES-SG system energy efficiency is further improved.