The invention discloses an open winding permanent magnet synchronous motor series compensation vector control system which is composed of a direct-current power source, a main converter powered by the direct-current power source, an open winding permanent magnet synchronous motor, a compensation converter powered by a power supply capacitor, voltage sensors arranged at the two ends of the power supply capacitor, a current sensor arranged on the stator side of the open winding permanent magnet synchronous motor, a speed sensor arranged on a rotation shaft of the open winding permanent magnet synchronous motor, and a controller controlling the main converter and the compensation converter. According to the open winding permanent magnet synchronous motor series compensation vector control system, the compensation converter which is arranged at the stator tail end of the open winding permanent magnet synchronous motor and powered by the power supply capacitor is controlled to equivalently change stator winding impedance, so that the power factor of the main converter approaches to or reaches 1; through cooperation control over the main converter and the compensation converter, distribution of active power and reactive power is changed, performance of the motor is improved, a flux weakening control area of the permanent magnet synchronous motor is expanded, and the operation range is widened.