The paper presents a methodical approach to the study of the dissipative function of the tribosystem. The significant parameters of the friction process are determined and the dependences of the stress on the actual contact spots, the rate of deformation of the materials of the friction surfaces, the deformable volume of the material of the friction surfaces when changing the design, technological and operational factors are presented. It was established that the greatest contribution is made by the average arithmetic deviation of the points of the profile of the friction surfaces and the average step of unevenness along the center line, and then by the physical and mechanical properties of triboelement materials (modulus of elasticity and Poisson's ratio). The obtained dependences of the influence of significant parameters of the friction process in tribosystems will allow to determine the distribution of the dissipation rate between moving and stationary triboelements, which will be shown in the second part of the paper. The work will be devoted to the calculation of the dissipative function of the tribosystem and the establishment of a correlation relationship between the specified function and the wear rate and the friction coefficient.