Abstract: For the symmetrical six-phase permanent magnet synchronous motor (PMSM) and three-phase PMSM series-connected system supplied by single inverter, the control current is transformed into the stationary coordinates composed of three mutually perpendicular subspaces through the decoupling transformation. The six-phase motor and the three-phase motor are controlled by current in the former two subspaces respectively. Furthermore, the mathematical model is transformed into the rotating coordinate system through rotation transformation. The vector control strategy is adopted to realize the independent control and decoupling operation. The experimental result shows that the symmetrical six-phase PMSM and three-phase PMSM series-connected system is able to achieve smooth operation and rapid dynamic response in which the status of one motor has no influence on the other.