In order to solve the problem of the current distortion under unbalanced voltage and the complexity of the phase-locked loop (PLL) of the grid-connected inverter, a strategy based on virtual synchronous generator (VSG) under unbalanced grid voltage without PLL is proposed. The control method of VSG under unbalanced grid voltage is detailed studied. An improved VSG control strategy based on PIR current control loop is designed to restrain current distortion effectively without changing output characteristics. Meanwhile, a VSG resynchronization control strategy based on virtual power is proposed to guarantee seamless switches between grid-connection mode and off-grid mode. The PLL is not used throughout the proposed strategy, which avoids the bad effect of PLL on control precision and response speed and makes the control system simplified in addition. Finally, a real-time simulation platform based on RT-LAB is built to verify the proposed control strategy.