Battery energy storage system(BESS) is a valid alternative to maintain the stability of isolated power system consisting of distributed power generation, such as wind power and PV power. With the development of distributed power generation technology, large-scale battery energy storage system (BESS) is applied in the power system. The operational principle of large-scale BESS and control characteristic of battery system were analyzed. To resolve low control accuracy problem caused by the inconsistent SOC and not pure inductance in the low voltage grid , a new method based state of charge(SOC) of battery system was proposed to share load power. The system simulation plate was built in PSCAD/EMTDC soft environment. The effectiveness of the proposed control strategy by the simulation experimental results.