In the optical storage DC microgrid in island mode, in view of the large inrush current problem of the inverter controlled by the optical storage VSG when switching from off-grid to grid-connected operation mode, a pre-synchronization control strategy based on secondary frequency regulation and voltage regulation was proposed. This strategy can adjust the large frequency and voltage fluctuations caused by active and reactive load changes under the independent DC microgrid of the optical storage. At the same time, it can complete the effective tracking of the grid phase before connecting to the grid, and reduce the impulse current when the optical storage microgrid is isolated and connected to the grid. The real-time digital simulation platform (RTDS) is used to simulate and analyze the proposed control scheme, and the simulation results verify the feasibility of the proposed control strategy.