In order to solve the problem of excessive deformation of sandy soil at road foundation caused by mining and automobile with heavy duty, we study the strength and deformation resistance of sandy soil under four different fiber lengths and blending amounts through triaxial compression test.Results show that the stress-strain relation of fiber-reinforced soil is approximately a hyperbolic function, in which the main failure form is swollen failure. With the increase of blending proportion and length of fibre, the mechanical properties of fibre-reinforced soil strengthen, but the angle of internal friction is barely affected. Finally, a fitting formula of cohesion vs. fiber length and mixing amount is obtained by multivariate regression analysis based on the 1stOpt experiment and the results meet the requirement of actual projects by comparison with measured data.