Large current harmonics and severe fluctuations occur in active and reactive power for single vector model predictive direct power control (MPDPC) of sixphase permanent magnet synchronous generator (PMSG). Aiming at these problems, a duty cycle synthetic vector MPDPC is proposed. By reconstructing the large and mediumlarge voltage vectors of the sixphase rectifier, twelve synthetic vectors are obtained, and the harmonic currents are effectively suppressed. On this basis, aiming at further suppressing the fluctuation of active and reactive power, a synthetic vector and a zero vector are used simultaneously in each cycle, and the optimal duty cycle is calculated according to the principle of deadbeat prediction of active and reactive power. Experimental results show that the proposed duty cycle synthetic vector MPDPC can effectively reduce current harmonics and power ripples.