The method of diagnosing various constructions of tribosystems by acoustic emission method is developed in the work. The development of the methodology is based on the following assumptions. The activity of acoustic emission during the operation of the tribosystem will depend on the rate of deformation of materials on the spots of actual contact. The total acoustic signal from the friction zone is formed as a result of the interference of the primary acoustic signals from the spots of actual contact with the friction surface, which correspond to the coherence condition. Based on these assumptions, the expression for calculating the informative frequencies that will be generated by the tribosystem in the process. The method of diagnosis contains the following steps: determination of informative frequencies on which it is necessary to register amplitudes; determining the magnitude of the amplitudes that carry the maximum information; distribution of the general acoustic signal on clusters and establishment of functional communication of values of a peak factor of clusters with values of coefficient of friction, speed of wear and time of running-in of tribosystems in an online mode. The use of the developed technique will increase the robustness of the method of diagnosing tribosystems and identify surface processes during wear.