Abstract: In this paper a method is present for the configuratinal optimization of structures subject to displacement, stress and buckling constraints u-nder multiple load conditions. To construct a new sequence of approximate problems, we expand the objective function into a incomplete second order Taylor series in which the cross terms are ignored, and expand the constraint functions into linear Taylor series in the mixed design variable space （the design variables of structural elements are reciprocal）. Then, a separable convex approximate problem is obtained, This approximate problem can be solved by a dual method of convex programing. Computational result for two trusses show that the method presented in this paper is very efficient.