Abstract: Breakage mechanics conceptualizes the geological materials as binary structural bodies consisting of bonded blocks and weakened bands. During their deformation the blocks break down gradually and turn to be weakened bands. In this paper, starting from the homogenization theory of heterogeneous materials, the evolution law of breakage parameter has been derived, and through an ideal brittle elasto plastic model the typical behaviors of geological materials of softening under low confining stress and hardening under high confining stress have been successful simulated.