Compared with the conventional pulse width modulation (PWM) technology, random PWM (RPWM) has effective ability of harmonic spectrum dispersion, which can reduce the noise of electromechanical load. The RPWM technology includes three basic methods: initial random switch modulation, and subsequent random pulse position and random switching frequency modulation. With the overall development of power electronics technology, RPWM has been gradually expanded from conventional carrier modulation to space vector modulation, the application prospect is increasingly broad, and the effect of power spectrum peak suppression is continuously improved. At the same time, new optimization schemes are put forward constantly, and the dispersion effect of harmonic and power spectrum is also continuously improved. The research history of RPWM is reviewed, the basic principles of some typical RPWM technologies are introduced, and the future research directions of random PWM are prospected, so as to provide a reference for further research of RPWM technology.