Abstract: On the assumption that the particle displacement caused by static stresses is finite displacement and the particle displacement caused by wave transmission is infinitesimal displacement, the theory of the nonlinear acoustoelasticity has been used to calculate the equivalent second order elastic constants of the plate with orthogonal static stresses acting on.The relationship between Lamb wave velocity and static stresses in metal plate is discussed.The result is valuable both in theoretical study and practical application, and can be the basis of stress measurement with Lamb wave.