An important task of modern metal production is the development and introduction of new technological processes of pressure working, combining a slight change in shape and dimensions of the workpiece with intensive deformation. These requirements are met by the process of equal channel angular pressing (ECAP). The analysis was made of the impact of technological regimes of equal channel angular pressing on the shape of the deformation zone, strain rate intensity, the degree of accumulated deformation, indicators of stress and damage in metal with ideal plastic properties and power-law hardening. Mechanics of equal channel angular pressing is examined by the use of methods of slip lines and the upper estimate, and damage calculation is based on the of ductile fracture mechanics in plastic metal working. Regularities of the ECAP process management and rational modes of deformation are found. The facts obtained were confirmed by the results achieved in the ECAP simulation process in the software package Deform-3D. The work shows new areas of the research of equal channel angular pressing, related to grain refinement and the study of the process of metal destruction. In particular, adjusting the strain rate of the process and controlling the temperature, it is possible to provide conditions under which the workpiece material is fully polygonized, new centers of recrystallization are formed, recrystallization processes of the unprepared metal structure (primary recrystallisation) are suppressed and conditions for grain refinement and obtaining the ultrafine metal structure are generated. The computer experiment carried out with the help of the software package Deform-3D confirms with sufficient accuracy the theoretical study of the ECAP.