Abstract: As the main bearing structure, the CNC gantry beam is the goal of high stiffness and lightweight design. In order to realize the lightweight design of the beam, ANSYS simulation platform is used to analyze and compare the static and dynamic results. The results show that the ten-type beam is better than the rat cage type in terms of deformation, stress and natural frequency, which has great optimization potential. Based on the response surface model and non-dominant ranking genetic algorithm. Under the premise of meeting the requirements, the beam mass was finally reduced by 335.5 kg, accounting for about 7.34% of the original weight, which provided a reference for the lightweight and high-performance design research of CNC machine tools.