More than half of all oil-gas reservoirs in the word are Naturally Fractured Reservoirs. Modeling of fluid flow in these types of reservoirs is challenging due to heterogeneity and anisotropy of their permeability distributions. This paper presents a method of determining distribution of fracture permeability tensor of fractured reservoir from maps of natural fractures by Discrete Fracture Network modeling technique. The method have been applied to obtain a new permeability distribution for simulation model of fractured basement reservoir of Bach Ho field in Vietnam, with the input parameters as aperture, shape, size, direction and permeability from interpretation of core measurements, well tests and well log data. The simulation model with new permeability distribution is evaluated by comparing with the initial simulation model. The result shows that the methodology is very promising in improving the agreement between simulated results and measured field data.