Abstract: Residual soil is one of special soils,of which engineering geological property is usually different because of its difference in origin of rock,geological environment and weathering condition.With field exploration,laboratory tests and in-situ tests,the physical and mechanical properties of the residual diorite in Jinan were studied thoroughly.The stratigraphic section of the soil can be classified as two layers on the perpendicular direction.Considering inhomogeneity of the residual soil mass and wide divergence of the value of mechanical properties,the authors suggest values of c,,a,Es,fak as a guideline for engineering practice.It was also pointed out that the interlayer and inhomogeneity of the weathering layers should be emphasized in design and construction when the residual diorite or one of the geologic layers is used for foundation of a structure.