Abstract: In the weak power grid environment of the islanded microgrid with heterogeneous distributed generators, the virtual synchronous generator（VSG） based on the phase difference control produces frequency fluctuation due to the periodic jump of the phase angle difference, and the coupling of the phase-locked loop（PLL） and the weak power grid affects it, which easily leads to the instability of VSG and even system collapse. Therefore, a pre-synchronization control strategy of VSG based on the virtual current is proposed. First, the jump mechanism of the phase angle difference is briefly analyzed to reveal its influence on the gridconnection process of VSG. Then, the input variable of the phase angle controller is improved based on the virtual current for eliminating the jump of the phase angle difference, to improve the frequency stability of the grid-connection of VSG and realize the pre-synchronization without PLL. On this basis, a small-signal model is established, and the effects of different parameters on the pre-synchronization process are analyzed, while reasonable controller parameters are designed to improve the dynamic performance of the system. Finally, the simulation on MATLAB/Simulink and the hardware-in-loop experiment on StarSim verify the effectiveness of the proposed strategy.