Soil-rock mixture is a kind of inhomogeneous material with macro geo-binary medium.It has different equivalent strength properties with different inner block distribution and different scale.Random model of soil-rock mixture was established by using the method of random aggregate structure（RAS）.The output of random model and formation of numerical model were carried out by compiling program.For an example

take the huge landslide of deposit body in the southwest China

it contains the typical soil-rock mixture.Random model with different scales was established after considering the factors of stone content and particle distribution;and a lot of numerical tests was carried out.We got its representative element volume（REV） scale of the mechanics property.By this step

the equivalent strength parameters was obtained;and its mechanical behavior and gradual damage modes were analyzed.It is shown that the soil-rock mixture has the REV scale and the REV scale in case is 1.0 m×1.0 m;based on this

the obtained mechanical parameters are useful.