The invention provides a method and a device for determining optional ranges of the virtual inertia and damping coefficient of a VSG (Virtual Synchronous Generator), and relates to the technical fieldof VSGs. The method comprises the following steps: acquiring relevant parameters of a VSG grid-connected system built from a VSG to an infinite grid; establishing a state equation of the VSG grid-connected system; determining a small signal equation of the VSG grid-connected system; determining a small signal space equation of the VSG grid-connected system; determining a transfer function of theVSG grid-connected system; determining a natural oscillation frequency function and a damping ratio function of the VSG grid-connected system; and determining the optional ranges of the virtual inertia and damping coefficient of the VSG according to the natural oscillation frequency function, the damping ratio function and a preset restraining condition which is relevant to the natural oscillationfrequency function and the damping ratio function. Through adoption of the method and the device, the optional ranges of the virtual inertia and damping coefficient of the VSG can be determined accurately, so that the running of the VSG is safer and more stable.