The paper is devoted to improvement of technique of designing of bearing structure of track machines bodies. The review and analysis of state-of-the-art of the mathematical programming theory and the optimal designing are done. The numerical optimization procedure for bearing structures of track machines bodies is proposed. The approbation of the proposed procedure is taken on the number of problems of structural optimization. The number of the mathematical aspects of implementation of the proposed procedure are investigated, particularly the algorithm convergence and the sensitivity analysis of initial designs. The deflected mode of the bearing structure of body of the ballast leveling machine SPZ-5/UA was investigated analytically (FEM study) and experimentally (trial running inspection on durability). The necessity of implementation of optimization of bearing structures of bodies is substantiated. The rational design of bearing structure of track machine SPZ-5/UA was obtained with the numerical optimization procedure proposed in the paper. The deflected mode of the rational bearing structure of body was investigated.