Virtual synchronous generators (VSG) have drawn a lot of attention since they can give microgrids inertial and damping properties. However, the grid environment will impact the phase locking accuracy of the phase-locked loop (PLL) during the microgrid's transition from island operation to grid-connected operation. Meanwhile, the typical pre-synchronization technique may lose control due to the significant phase angle difference between the microgrid and the grid, endangering the frequency safety of the microgrid operation. This study suggests a VSG-based pre-synchronization control method with linear active disturbance rejection control (LADRC) to address these issues. Compensate the angle and amplitude of the output voltage to track the grid voltage using the droop curve. As a result, the properties of linear active disturbance rejection are used to achieve a seamless transition from island operation to grid-connected operation under various phase differences. At the same time, the microgrid frequency variation range during the pre-synchronization process is limited. Finally, the MATLAB/Simulink simulation results are used to confirm the efficiency of the suggested control approach.