Abstract To reasonably evaluate the support capability of grid-forming energy storage in power systems characterized by “double high” characteristics, it is essential to investigate the factors influencing the virtual inertia of grid-forming energy storage. This paper delves into the relationship between two control strategies of grid-forming energy storage and virtual inertia from an energy perspective. Initially, the operational principle and technological advantages of grid-forming energy storage are analyzed. Subsequently, based on the principles of two grid-forming control strategies, mathematical models for both types of grid-forming energy storage are established, elucidating the physical significance of virtual inertia in grid-forming inverters and revealing the adjustability of virtual inertia. Finally, a microgrid simulation system is constructed in PSCAD to validate the theoretical analysis.