A motor driver using a motor magnetic pole reference controlling mechanism is provided. A motor position detecting circuit detects a rotor of a motor to determine a plurality of magnetic pole positions to which the rotor of the motor is switched respectively during a plurality of time intervals. A reference magnetic pole switching circuit selects one of the plurality of time intervals according to a change in rotational speed of the motor over time. The reference magnetic pole switching circuit uses the magnetic pole position to which the rotor of the motor is switched during the one of the plurality of time intervals as magnetic pole reference data. A motor driving circuit drives the motor according to the magnetic pole reference data from the reference magnetic pole switching circuit.