The crossbeam is an important part of machining tool, and the stiffness of crossbeam has great impact on machining accuracy, therefore, optimization design is necessary for the crossbeam to obtain its good static and dynamic characteristics. Six kinds of rib structure were designed and preliminary screened out four kinds of them. The orthogonal experimental method was carried out with three levels and four factors ,which took the crossbeam’s rib structure, the rib thickness, the angle of supporting ribs on guide-way as design variables, and took the crossbeam’s quality , the maximum coupling deformation, the maximum coupling stress, the first-order frequency as objective functions; Grey correlation method and the combination weighting method were used to the data processing of finite element analysis to obtain the optimal parameter combination. The results show that the crossbeam with "井" type rib structure, rib thickness of 25mm, the supporting ribs on guide-way tilted 45 ° is the optimal solution. Compared with the original design, the beam deformation reduced by 7.36% and the first-order frequency increased by 2.91%, while the quality reduced by 466kg. It expanded the applications of orthogonal experiment, grey correlation method and the combination weighting method, provided a useful method for the design of other machine parts.