The dual-buck topology overcomes the straight-through problem of the traditional bridge topology in the same bridge. It is used in three-phase grid-connected inverter can avoid the increase of current harmonics caused by the dead-time. So this paper presents a new method of combining space-vector algorithm with one-cycle control, the AC voltage of three-phase bus bar is divided into six regions which are all in one cycle and a one-cycle control model is built for each regions. The three-phase dual-buck grid-connected inverter used this control method can possesses fixed switching frequency, high efficiency and high reliability. The validities of control method have been proved by Saber. At last, making a 10kW prototype whose result shows that the inverter possessed satisfied steady state performance and can transmit electric power under high power factor.