When the loads in three phases are unbalanced, the traditional inverter can not make the output voltages balanced. So a 3-phase 4-leg structure is used for controlling the zero-phase voltage and current to reply the unbalanced loads. In this paper, by decoupling the 3-phase output voltage and adding in the double loop control of voltage and current, the space vector modulation to the inverter control stability is enhanced and the dynamic response characteristic is improved. And then, Matlab/Simulink is applied to modeling and simulating, and the simulation model is set up which make the simulation achieve a desired effect. According to the algorithm, DSP is programmed and by observing SVPWM waveform, reasonability and availability of the algorithm are verified.