The paper presents a microgrid energy management strategy (MEMS) for a Medium-Voltage Isolated microgrid, which is China's 10kv island microgrid demonstration project to accommodate the increasing power needs of customers and solve problems of island power supply. When the SOC is restored in security zone, the energy storage system (ESS) would increase the sensitivity and adjust the maximum charging or discharging power to avoid repetitive fluctuations. According to the system's control algorithm, when the microgrid load rate is normal, or above the upper limit, or below the lower limit, the MEMS system can start or stop some micro sources, charge or discharge battery, to maintain the stability of the system's voltage and frequency and to confirm the microgrid stable and effective. The effectiveness of the proposed strategy is verified by experimental results.