Aiming at the problem that the output voltage quality of threephase inverter was easily affected by harmonics when the output side of the threephase inverter was connected with nonlinear load, a voltage control method based on the reducedorder resonant controller (RRSC) was selected. Compared with the resonant controller (RSC), the RRSC could separate the positive and negative order and then deal with them separately. Moreover, the RRSC had less computation and higher efficiency. In order to further reduce the harmonic content of output voltage, the RRSC was further improved and applied to threephase inverter voltage control. Finally, the proposed control method was verified by simulation and compared with the RRSC in detail. The results showed that the proposed control method was effective.