The off-grid switching strategy of solar-storage microgrid is an important support to ensure the smooth operation of the grid. Aiming at the problems such as deviation of voltage amplitude, phase and frequency between the microgrid and the large power grid, based on the V/f control of the energy storage inverter, the large power grid voltage is used as the reference value of the controller to simply the structure of the pre-synchronization control link. An improved pre-synchronization method is proposed. Based on the negative sequence current change from off-grid to grid-connected, the islanding detection method is explored to determine the off-grid signal. Considering the output characteristics of photovoltaic power supply and off-grid switching operation, a control mode of two energy storage units is proposed. The switching sequence of V/F and P/Q control modes of different energy storage units is determined. According to the time-sharing conversion, the impact of system switching is reduced. Off-grid switching test, parallel-off-grid switching test, three groups of optical storage and output power grid-connected strategy simulation comparison tests are designed. The results show that off-grid voltage deviations of amplitude, frequency and phase angle are less than 1%, ± 0.1 Hz and 5 ° respectively with improved pre-synchronization control, and the structure is more simple. Based on the switching strategy of the two energy storage units, the switching time of the off/grid mode is shortened and the impact is reduced. The result verifies the effectiveness of the proposed improved pre-synchronization method and the switching strategy based on the two energy storage units.