Nowadays, the railway transport infrastructure in Ethiopia is one of the major issues inrnrelation to the development of the country. To strengthen this infrastructure, related rnresearches must be conducted at the beginning or during the construction of the sector. rnThis paper is mainly concerned on optimizing a railway flat wagon underframe structurernthat has been subjected to a multi objective optimization to improve stiffness to weightrnratio. rnIn order to perform structural design optimization with a finite element method (FEM), arn3D model of the freight wagon underframe has been prepared by using a 3D modelingrnsoftware CATIA V5R20 software. The discreet FEM model has been imported in tornANSYS 14.5 workbench, and optimization has been done on the frame structure basedrnon the initial parameters by using multi objective optimization techniques (ANSYS). rnThe result has been showed in the form of graphs which relates the input and outputrnparameters with the design variable. After graphical interpretation, structural analysis isrncarried on by using ANSYS; just to check how far the input and output parameters arernimproved at the highest loading conditions. rnObserving the optimization results and static simulation effects of the existing model atrnthe highest loading conditions, it has been conclude that the center sill is a shell elementrn(note a solid element) and the optimum plate thickness for the center sill is 23mm. Thernfinal product of the optimization process is a low weight underframe structure whichrnreduces 18.02% of the overall weight of the wagon and 9.01% to 12.614% of reduction inrnpower consumption. As a recommendation it is suggested that dynamic effects on thernunderframe should be done for safety and is recommended as future work.