The invention relates to a high-accuracy rotational speed controller of a phase-locked motor. The high-accuracy rotational speed controller comprises a first counter, a second counter, a third counter, a proportion integration differentiation (PID) controller, a pulse width modulation (PWM) controller and a Hall sensor, wherein the counters are used for counting a period of an external output reference square wave signal SYN, a period of a Hall signal and current phase difference between the square wave signal SYN and the Hall signal according to a frequency CLK, the Hall period counting valuen' is subtracted from the SYN period counting value n to obtain a difference value es used as rotational speed part control quantity, reference phase difference 0 is added to the current phase difference phaseErr, phase part control quantity ep is obtained after graining k, the sum of the es and the ep is used as total control quantity e to be input to the PID controller, an output is finally obtained by the PID controller, and the motor is controlled to rotate by the PWM controller. On the basis of traditional rotational speed feedback, a phase-locked loop is additionally arranged, relatively high rotational speed accuracy of the motor is ensured, the phase of a reference signal also can be traced constantly, and the problem that an angle error rotated by the motor can become large withtime accumulation due to rotational speed deviation of a pure-rotational speed control ring is solved.