By combining the finite element method with linear programming，finite element & linear programming method (the FE&LP method) has been developed and systematized in order to solve optimal systems of differential equations with both equality or inequality constraints and an objective function. Such systems are frequently encountered in various engineering and scientific problems of control and optimal design. In this study the application of the FE&LP method to optimization of combined spring systems is presented. The method makes it possible to obtain not only the optimal controllable loads to meet with the imposed upper limits of stresses，but also the nodal displacements in spring systems. The method may become one of the most useful techniques in optimal design of structural systems.