In the large-scale application of new energy, energy storage device acts as a kind of controllable power supply. It has the advantages of large amplitude of peak regulation and fast response, so it plays an important role in ensuring the normal operation of microgrid. A two-stage energy storage inverter is introduced: one stage is the grid side converter which is composed of three-phase full control bridge, and the other stage is the DC converter which is composed of three interleaved parallel circuits. Then, the control principles of the energy storage inverter in on-grid/off-grid operation mode and the key points of switching between on-grid/off-grid are introduced. The MATLAB simulations show that the proposed control strategy can realize the normal operation of on-grid/off-grid and the smooth transition of switching between on-grid and off-grid, and the DC converter can improve the total output current capacity by three interleaved parallel circuits and reduce the total output current fluctuation by carrier phase shifting. The energy storage inverter can reliably realize the on-grid/off-grid operation control of microgrid. The continuity of renewable energy power generation output power is effectively improved, and the technical support for the further development of new energy field is provided.