Abstract: Based on the statistic rock fracture data in situ, in the process of 3-D fracture network simulation technique, the method for the 3D equivalent conductivity of fracture network and porous media is the key problem of rock hydraulics. However, the porous media flow model is the most practical in the hydraulic geotechnical engineering, and the conductivity of fractured rock is very difficult to be specified. According to the character of conductivity tensor, equality in flux and the same condition in the boundary, a new method of second-order conductivity tensor is derived from representative volume element of 3-D fracture network simulation. As the result, an example is presented to prove that the method is reasonable. The method proposed in the paper provides a practical technique for exterminating permeability tensor of fractured rock by fracture survey, and this will promote the developing of rock hydraulics.