Abstract：The microstructure of rock is researched by means of scanning electron microscope(SEM)，and a damage model of rock microstructure is proposed. The damage evolvement and breakage process of stratified rock are studied；and the constitutive equations and damage equations are established. The damage variable and damage enlarging variable are used to set up the equations for the whole evolvement of damage and to describe the initial approximate linearity and later accelerating process in rock mass. The damage evolvement and breakage process of rock mass are divided into three phases. The damage evolvement，breakage characteristics and stability of stratified rock are analyzed；and the regularity of damage evolution of rock is explained. The research shows that the appearance and breakage of stratified rock are related not only to load and its rate，but also to the regularity of damage evolution of each rock bedding，the angle of load with stratified rock，and the microstructure characteristics of rock. Therefore，the influence on the in-situ stratified rock is remarkable.
