Abstract: Heterogeneity is one of the important properties of rock mass. Heterogeneity is widespread in rock mass from the material composition to structural characteristics to micro-macro mechanical behavior. On the basis of reviewing the existing researches,the causes,characteristics,mechanical effects and temporal and spatial evolution of rock mass heterogeneity are described from three different scales including micro heterogeneity,structural heterogeneity and macro heterogeneity. The relevant study methods and the different manifestations of heterogeneity at different scales are introduced. The study of rock mass heterogeneity is an extension of the theoretical system of engineering geomechanics of rock mass. The multi-scale research method has also become an effective means to fully reveal the deformation and failure mechanism of rock mass.