Abstract: The frequency spectrum analysis of pyroelectric voltages generated in three typical friction pairs was carried out.On the basis of this analysis, friction experiments applying various electric signals into these three friction pairs were made. The results showed that various electric signals have various effects on the friction force. They make the friction force decrease. The decreasing degree is related to the amplitude, wave shape and frequency charac teristics of pyroelectric voltage. This work provides an important basis for the technology of controlling friction with applied voltage.