The invention relates to a rotation speed and position detecting method for an outdoor fan of a DC permanent magnet synchronous motor (PMSM), belongs to the technical field of obtaining rotation speed and position of the motor, and aims at solving the problems that rotation speed and position detection for the outdoor fan of an air conditioner at present is inaccurate, and a concrete method for detecting forward and backward rotation of the motor lacks. The method comprises the following steps that a phase voltage value between a three-phase back electromotive force of the motor and a central point is obtained; According to a time difference between first zero-crossing time and second zero-crossing time of the phase voltage value of the three-phase back electromotive force, angles corresponding to the zero-crossing time of the phase voltage value of the three-phase back electromotive force is obtained at the same time, and position information of a motor rotor is further obtained; and the rotation frequency of the motor is calculated via phase-locked loop control. The method is suitable for the air conditioner.