Aiming at the special requirements of remote areas or independent power supply military sentry posts, the application of hybrid energy storage system in low-inertia military sentry post power grid is studied. The inertia dynamics and frequency control mechanism of the system are analyzed, and how the hybrid energy storage system simulates the synchronous generator is clarified. The application advantages of the hybrid energy storage system compared with the single battery energy storage system in key issues such as frequency regulation, island operation and grid resynchronization are discussed. The results show that this technology is of great significance for improving the stability of power grids in remote areas, ensuring the reliable operation of military facilities and promoting the transformation to a sustainable energy pattern.