A rotating speed detection device based on power supply control and output pulse frequency comprises a rotating speed sensor, a pulse shaping and amplification circuit, a microcontroller module, and a display module. The rotating speed sensor is connected to the microcontroller module by means of the pulse shaping and amplification circuit. The display module is connected to a corresponding port of the microcontroller module. The rotating speed sensor comprises a light source emitter, a rotating gear, and a photoelectric sensor. The light source emitter and the photoelectric sensor are disposed at two sides of the rotating gear. The rotating speed detection device has a simple structure and high measurement precision.