When inverter is connected to utility grid, if the voltage distortion of grid is severe, it can result in a significant number of harmonics in the grid current. Gallium nitride(GaN) based micro-inverters was generally operated under discontinuous current mode(DCM), resulting in time-varying modulation gain. As a result, it is difficult to employ the conventional grid voltage feedforward(GVF) scheme in s domain to suppress the harmonics of the GaN-based DCM grid-tied inverters. This article proposes a GVF scheme for DCM inverters based on the time-domain equivalent circuit, which significantly suppresses the grid current harmonics of the GaN-based DCM grid-tied inverters, especially under the condition of grid voltage distortion. The experimental results demonstrate that by utilizing the suggested scheme, the total harmonic distortion(THD) of the grid current can be reduced by 40% across the entire power range.