This paper investigates energy storage configuration strategy for virtual synchronous machine (VSM). The proposed VSM provides virtual inertia and damping to maintain stability of grid. Virtual inertia and damping need to be established by energy storage system (ESS). So that a strategy of energy storage configuration has been investigated through theoretical analysis and simulations in this paper. In addition, this paper also proposed influences of virtual inertia, damping factor and reference of reactive power on energy storage configuration. Simulation results verified the proposed energy storage configuration strategy.