A microgrid which integrates and optimizes resources within the goal of dual-carbon and new power system construction will be an important carrier for grid companies. The microgrid supports grid-connected or off-grid operation, and its off-grid operation can improve the reliability of power supply. This is an important feature of the microgrid. The off-grid microgrid requires a suitable steady-state control strategy to ensure long-term stable operation. At present, some energy management methods that rely on predictive information and use fuzzy intelligent algorithms will produce greater state control error in the actual long-term operation of the microgrid. In order to better solve the problem of quantitative calculation of power and electricity balance during off-grid operation of the microgrid, and to improve the accuracy of off-grid steady-state control, the real-time steady-state coordination of an off-grid microgrid based on master-slave control of the energy storage battery state of charge is studied. The control strategy puts forward an accurate engineering calculation method for the control node value of the energy storage state of charge in key operations such as intermittent power supply adjustment, load adjustment, and microgrid outage in the off-grid active power coordinated control of the microgrid. The specific application of coordinated control strategy is carried out for an actual microgrid application project. Simulation and actual operation prove the effectiveness of the control strategy and calculation method. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. SGJS0000DKJS1901020).