Abstract: To reflect well the nonlinear deformation character of soil during excavation, power function was employed to describe the process of tangent modulus decay with the principal stress difference decreasing during the shearing process of soil. The mathematical expressions between principal stress difference and strain were attained by integration, which was consistent with the requirement of general soil model. The expressions with different power exponents could fit stress-strain curves of triaxial test. Based on the method defining by parameters of Duncan-Chang model, the parameters of model were put forward. On the platform of a general finite element software the computing programs for the model were redeveloped, which was employed to precast deep excavation deformation. The results show the model proposed can predict better the enclosure deformation than Duncan-Chang model.