Abstract: As a coupling body of soils and rocks,soil-rock-mixture has the inherent unique properties of inhomogeneity,discontinuity and it is very difficult to gather samples to study its properties.Soil-rock-mixture is a typical porous medium,and its seepage is closely related to the particle-size,void ratio and particle shape.Based on the lab orthogonal tests,using self-manufactured constant head permeameter,the effect of gravel content,void ratio and particle shape on the coefficient of permeability of soil-rock-mixture was studied.By orthogonal tests,the influence of three factors on the coefficient of permeability of soil-rock-mixture,the significance of different factors was determined.A formula for calculating the coefficient of permeability of soil-rock-mixture was proposed and was verified by the experimental results,thus a concise and useful computational tool for the theoretical calculation of coefficient permeability of soil-rock-mixture was offered.