Abstarct: According to recent studies, the method of discrete fracture network (DFN) In order to build a model similar to the structure of the rock mass, In other words, the structure of fractures in the rock mass and fractures modeling fluid flow is optimal. In all rock engineering issues, particularly the study of fluid flow through the jointed rock masses, describing the fracture geometry and geometric simulation of rock mass and the main stages of the study. According to the survey in fluid flow in rock mass, including the most influential geometrical parameters can be influenced in the hydraulic conductivity of the rock mass fractures, can be noted oreientation, trace length or size, aperture, density and intensity of fractures. To simulate the random fracture rock mass by DFN method, Verification of field data available and determine the statistical distribution functions of the geometric parameters of fractures is essential. in this research, with a focus on rock mass of the Parsian reservoir dam, to build a geometric model of the rock mass hydraulic fractures using a discrete fracture network will be discussed. To build the model DFN, the joint sets rock mass by dips software and using field observations conducted, separation and characterized. Then, by the Easyfit and Minitab softwares, for each geometric parameters, statistical distribution functions are defined. Using data obtained from the process listed and commercial software 3DEC, real DFN model of rock mass made and presented. The DFN model and two-parameters cubic model as basis of the hydraulic analysis and empirical relationships presentation are used. Finally, relation to estimate permeability baxsed on matrix aperture and fracture frequency in the cubical model In the form of an empirical equation is presented.