The invention discloses a method for compensation and handling of asymmetric sag of a power grid based on negative-sequence current. The method comprises the following steps of detecting voltage sag of the power grid through a grid-connected inverter; and delivering the negative-sequence current to the power grid through the grid-connected inverter so as to reduce unbalance degree of power grid voltage when the voltage sag of the power grid is detected, wherein the grid-connected inverter delivers the negative-sequence current to the power grid based on calculation of the following equation, I<->d<-> and I<->q<-> represents components of the negative-sequence current on the d-axis and the q-axis of a negative-sequence rotating coordinate system respectively, KN represents rate adjustment coefficient, Ed<-> and Eq<-> represents negative-sequence components of the power grid voltage on the d-axis and the q-axis of the negative-sequence rotating coordinate system respectively, the Erated represents rated voltage of the power grid, and Irated represents rated current of the grid-connected inverter.