The invention discloses a VSG control method under a grid voltage symmetrical drop fault, which includes the following steps: S1, grid voltage information at a tie line is collected and transmitted to a local controller of a VSG in a micro grid; S2, active and reactive power reference instructions and a voltage reference instruction are calculated when a grid voltage symmetrical drop fault is detected; S3, a grid-connection small signal cable at the operation point of the fault is established, control parameters satisfying given dynamic performance and stability performance indexes are calculated, active power and voltage rated values are synchronously switched to the active power and voltage reference instructions, and the control parameters are switched; S4, the local collector collects local voltage and current information and establishes a voltage loop control model, a fault current limiting control model and a current loop control model; and S5, when the fault is detected to be eliminated, smooth transition from a fault state to a normal state is realized by adjusting the phase angle. Smooth and fast transition of the VSG from a fault operation state to a normal operation state after recovery of grid voltage can be realized.