Abstract: In view of problems of complex control and multi-harmonic of traditional inverter control strategy of grid-connected photovoltaic system, the paper proposed a direct current control method of grid-connected photovoltaic inverter system based on grid voltage orientation and gave design of hardware and software of three-phase grid-connected photovoltaic inverter system taking TMS320F2812 as main controller. The direct current control method uses zero cross detection circuit to measure zero cross time of grid voltage to gain rotation angle of grid voltage at zero cross time, so as to get amplitude and phase of output voltage of inverter, and uses SVPWM to control on-off of IPM to make inverter output voltage with above amplitude and phase, so as to realize grid-connected generation function with unity power factor. The experiment result showed that the direct current control method is simple, output current of inverter keeps same frequency and phase with grid voltage, and grid-connected power factor is close to 1.