Abstract: Study of epigenetic structure of rockmass is very important for understanding the structure of valley rockmass, constructing structural model of the rockmass, and its stability evaluation. In the area of Guandi Hydroelectropower Station, the epigenetic structures intensely developed, distributed regularily. In this paper, the authors study the regularity of spatial distribution and the association pattern of the epigenetic structures by analysis of the distribution of deformation and fracture trace, discuss their formation mechanism in connection with geologic physiological evolution mechanism, and construct the basic model of epigenetic structures of rockmass in the dam area.