A controlling system for a pole change electric motor of the type wherein the polarity of electric currents flowing through some of stator windings is changed to change the number of poles thereby to vary the rotational frequency of the motor. The system comprises a reactor which is connected, during running of the motor at a high speed, in series to a power circuit for supplying power to the motor, whereby the motor is driven by way of the reactor when the motor is changed over from a low to a high speed running.