The energy storage system is mainly composed of the following three parts, the power conversion system (PCS), battery management system (BMS), and energy management system (EMS). Among them, EMS is the core of the energy storage system. EMS needs to decide when to charge or discharge and monitor information such as the fire protection system, access control system, and ambient temperature and humidity in the facility. Good data transmission must be maintained between the equipment and the EMS. In the power system, the grounding system stabilizes the potential, discharging static charges, lightning current discharge path, grounding the equipment shell, and providing reference potential. If the grounding system of the energy storage facility is poorly designed, the noise generated by the PCS may cause electromagnetic interference to the communication line during the switching operation. In severe cases, the energy storage system will be temporarily disabled. This study analyzes the transient voltage variation at the grounding point when the ESS is connected or disconnected from the grid under different grounding methods. Referring to the grounding methods such as TT, TN, and IT in IEC 60364 standard, and analyzes in different ground impedance. The energy storage system model is established with EMTP-ATPDraw. After simulating various scenarios, a grounding method with low ground potential variation is proposed.