Abstract: A back EMF measuring method for multi-phase BLDC motor is proposed, which includes a driving process and a measuring process. The driving process energizes a plurality of phase windings of a detected motor by driving signals generated by a computing unit to rotate a rotor of the detected motor to a predetermined speed. The measuring process selects one of the phase windings as a target phase winding, continuously sends the driving signals to the phase windings other than the target phase winding but stops the driving signal sent to the target phase winding by the computing unit, and measures the back EMF of the target phase winding by a signal sensing unit.