In this paper, a procedure on the construction of an equivalent beam model is proposed. Firstly, full order model(FOM) is reduced by linear vibration modes and modal derivatives. And the reduced order model(MDROM) is tested with various loading and boundary conditions. By using various load cases and the time history of MDROM, equivalent nonlinear stiffness matrices are approximated in terms of quadratic and cubic. The modal derivatives-based equivalent model(MoDEM) can be constructed by the equivalent stiffnesses. The efficiency and performance of the MoDEM is verified by comparing with full order model.