Abstract: In order to make full use of the waste slag and stone, the rock-filled embankment has taken one kind of ideal embankment form in highway in mountain area. To ensure the stability, it is urgent to study this material. This paper studies the effect of grain composition and roughness to the specimen property. It is based on the large scale triaxial test with the samples from Ya-Lu highway. It examines the grain roughness effect with DEM to fit the properties of graded gravel material under the large scale triaxial test. The paper introduces the principle of the fitting of the sample grain shape and roughness and presents the generation process of the graded gravel rock with numerical samples in details. According to the numerical process and results, the samples with clumps can simulate the Skeleton-pore structure of the gravel realistically. The distribution of the contact force is very reasonable and uniform before loading. Mosaic texture between clumps can tremendously improve the strength of the numerical sample. Deformation process reflects the irregular intergranular bite and sliding characteristics. Sample strength and grain roughness(namely the D4 value) also have a linear proportional relationship. Sample initial coordinate number is one of the decisive factors for the friction angle. The law of coordinate number of the sample with clumps varying with the axial strain development reappears the microscopic mechanical properties of the elastic deformation for the granular material.