The problem of creep and long-term strength of metallic materials and alloys is considered. This problem is demanded in such important fields of modern engineering, as thermal and nuclear power plants, aircraft and spacecraft, etc. The damage conception was introduced in the mechanics of materials to describe long-term strength under conditions of high-temperature creep. In this paper is proposed to determine the damage parameter changes from experimental high-temperature creep curves. Therefore, only one kinetic equation for the creep rate for the case of a compressible medium is formulated. The continuity parameter is determined from this kinetic equation and depends on the creep rate and creep deformation. Similarly, the changes in the continuity parameter are determined by the Rabotnov solution. It was obtained that for the case of a compressible medium, a more intense accumulation of damage and, correspondingly, fracture processes are observed, compared with the Rabotnov solution.