This paper covers optimization techniques for trusses to find the most efficient cross sections and configuration of joints. The improvement will be achieved by applying changes in one or both of these parameters. Objective functions for optimization are weight and the deflection of the truss's joints. For optimization of both weight and deflection the MOPSO method is used. This is a powerful method that enables the optimization of huge trusses. The former methods for optimization of the shape or size of the trusses, was done separately and as a single objective while this paper covers a new way via multi objective methods. For proofing the ability of the represented method in this paper, some standard examples are compared. The comparison of the results shows good accuracy and desirable verity of pareto front.