Abstract: The rock masses in nature usually contain a large number of discontinuities, which results in the anisotropy of rock masses. As one of the important parameters to evaluate rock quality, the generalized RQDt is widely used in rock masses engineering.3D stochastic discrete fracture network method and scan line method are combined to study the spatial distribution regularity of rock quality in different directions. The suggested method is used to study the spatial distribution regularity of dam foundation. Specific steps are as follows:Firstly, based on the probability distribution functions and corresponding statistical parameters investigated in field, 3D stochastic discrete fracture networks are randomly generated using the Monte Carlo Method. Secondly, lots of generalized RQDt can be calculated by setting measuring points and measuring lines. Thirdly, the spatial distribution regularity of rock quality in different directions can be described according to the spatial distribution map. The results indicate that the proposed method is valid and useful for describing the spatial distribution regularity of rock mass quality.