Abstract: For the extreme difference in characteristics between “soil” and “rock” which compose soil-rock mixture (S-RM), the physical and mechanical characteristics of S-RM are more complex than those of the general soil or rock. And for the insufficient recognition of S-RM, different degree problems will be met in many engineering projects. Especially in the southwest of China, with the building of large scale hydropower stations, the S-RM is usually the main geomaterials for slopes, landslides and dam basements in the reservoir area. Permeability is one of the important study contents of the physical characteristics of geomaterials. There is a close relationship between the permeability of S-RM and its meso-structure, and it is of great value to study the S-RM if we can build this relationship. The statistics, geometry, random simulation technique and so on are employed, and a software (R-SRM2D) is developed for the generation of random meso-structure of S-RM based on arbitrary convex polygon blocks and elliptic blocks. Using R-SRM2D, many samples with different rock block proportions, spacial distributions, and rock block size distribution, etc. are generated, and based on the numerical tests, the characteristics of the meso-seepage field, the mechanism of seepage failure and the quantitative relationship between the maro-permeability coefficient of S-RM and its meso-structural characteristics are studied.