Abstract: In the main frame of electronic universal testing machine, the three transverse beams account for the main weight and cost of the main machine. Most testing machine manufacturers utilize solid thick iron plate or cast iron to make the transverse beams, and the two methods have their own advantages and disadvantages. In the paper, the transverse beams of a 100kN electronic universal testing machine are optimized, and a fabrication method involving the combination welding of Q235A iron plates is used to make the beams. After optimization design and finite element analysis, the optimized new transverse beam is more effective in weight reduction and reasonable in mechanical properties than the existing beam. Compared with the existing main frame, the weight is reduced by about 19.67%, the cost is saved, and the stiffness of the whole system is increased by about 5.3%.