We present a three-phase four-leg matrix converter circuit topology, which can be used as three-phase four-wire AC voltage source to power the load imbalance. For the matrix converter topology, a novel indirect space vector modulation strategy is proposed, and the switch vector synthetic formula are deduced, giving a range of options, duty-cycle calculation and output reference voltage settings. Finally the new circuit topology for the simulation is studied. The results show that the circuit topology under three-phase unbalanced load can ensure sinusoidal output voltage waveform and stability.