A grid-connected control method based on a virtual synchronizer is provided. The method includes: detecting whether a first deviation between an output voltage of an inverter and a voltage of a grid exceeds a first set voltage threshold, and adjusting a set output voltage of the inverter if the first deviation exceeds the first set voltage threshold, so that the first deviation falls within the first set voltage threshold; detecting whether a second deviation between an output frequency of the inverter and a frequency of the grid exceeds a first set frequency threshold, and adjusting a set output frequency of the inverter if the second deviation exceeds the first set frequency threshold, so that the second deviation falls within the first set frequency threshold; and controlling the inverter to connect to the grid. A grid-connected control device based on a virtual synchronizer is further provided.