Abstract: A computational procedure named NCP function method for sensitivity analysis of elastoplastic structures is developed based on the complementarity formulation of elastoplastic structural analysis.By introducing the NCP function,a system of nonlinear equations is formulated for the complementary node.The design sensitivity formula of elastoplastic structures is derived by directly differentiating the nonlinear equations with respect to the design variables.Discontinuities of the design sensitivity coefficients at material transition points can be accurately described,and the iterative procedures to compute the jumps of the sensitivity coefficients are no longer needed in the newly proposed sensitivity analysis model.Numerical results demonstrating the validity of the approach are reported.