The geometrical and stress similarity cannot be both satisfied in traditional soil model test. We put forwarda new soil slope model applied with tangent directional seepage and normal directional stress. For colluvial slope model of small thickness, the similarity of stress along slope and vertical to slope surface were satisfied respectively by applying seepage force and surcharge load vertical to the slope surface, thus self-weight of the soil slope model can be similar to that of the in situ slope. Numerical analysis was conducted to compare the stress and strain similarity of in situ slope (thickness of 3 meters) and slope model (thickness of 0.3 meter). The calculated result shows the area with stress and strain similarity in the soil slope model; the distributions of maximum shear stress and strain in the model and the in situ slope are similar, with the error less than 10%. The results verified the feasibility of the model test method.