The article examines a new approach under the identification of the process of crushing in a jaw crusher. The capacity of a crusher corresponds to its output and is determined by the height of material elementary volume displacement per one pace of movable jaw. The value of elementary volume is defined by the shape of the crushing space, the pace size of movable jaw, inclination angle of movable jaw, distance between movable and unmovable jaws, movable jaw oscillation frequency, size of the crushed material, and its physical and mechanical properties. There is a section in the crushing space along the height, which determines the capacity of a crusher depending on the size of the crushed material. Maximum capacity of a crusher can be obtained under the higher speed of material motion in a given section of crushing space. In the process of scientific investigations the influence on the capacity has been determined, consumed for the crushing, power and degree of the crushing of the main changing parameters, determining the value of elementary volume of movable material. Mathematical description of the process of crushing in jaw crushers has been obtained. As the result of experimental investigations it has been determines, that under the material crushing in a crusher there are the elements of smashes on the lumps of material, the action of which increases with the increase of the oscillation frequency of the movable body of a crusher, and the degree of crushing increase. The analysis of existing methods of identifying the process of crushing in jaw crushers has revealed the disadvantage in the description of the strength of the crushed materials, taking into account compressive resistance and ignoring percussion action on the crushed material.