In fractured rock masses when the permeability of intact rock matrix is negligible, the main part of fluid flows through a connected Discrete Fracture Network (DFN) model. Practical and theoretical studies show that the discrete fracture network models are the most appropriate model for fluid flow and particle traort modeling in fractured rocks for which an equivalent continuum model is difficult to establish. The FRACIUT 2D and FRACIUT 3D codes have been developed for generating of 2D and 3D, DFN models based on the density function of geometrical properties of fractures such as fracture location, aperture and orientation using Monte-Carlo method. A large number of 3D DFN realizations in different block sizes and fracture shapes such as elliptical, circular or polynomial may be generated and visualized in FRACIUT 3D code. Down-scaling modeling with different sizes in different orientation is also available in FRACIUT 2D models. For fluid flow simulation in 2D and 3D fractured rocks two different numerical codes FLUIUT 2D and FLUIUT 3D codes were developed respectively. Both codes are able to determine the intersections between the fracture traces and planes. All fracture networks in in 2D and 3D are regularized and therefore single, isolated and not connected segments which do not have any contribution in fluid flow are discarded. A pipe network modeling are considered for fluid flow modeling in FLUIUT 3D codes in which an equivalent pipe is located in DFN models instead of each fracture plane. Using numerical Discrete Element Method (DEM), fluxes are determined and permeability tensor of fracture network is calculated. The calculated permeability by FLUIUT 2D is well fitted with results of fluid flow simulation using commercial code UDEC. It has also shown that the calculated permeability by FLUIUT 3D code when the polynomial fracture shape is considered is significantly different from the circular shape which is most popular form in other commercial codes.