In order to ensure the machining accuracy and cutting efficiency,the moving parts of a machine tool not only need to be of higher stiffness in the cutting process,but also is required to have a light weight so as to reduce the inertia and deformation due to the self-weight during the fast moving process.As a typical design example,the headstock of a bevel gear grinder was studied.A flexible multi-body dynamics finite element model including the components of headstock,electric spindle grinding head,ballscrew and so on was established.The flexible multibody system dynamic analysis was combined with the static structure optimization theory based on the equivalent static load theory and the topology optimization design was performed on the headstock.Compared to the traditional topology optimization design of the headstock based on the static load,the proposed lightweight design method is suitable for moving parts of machine tool.The results show that the weight of the headstock is decreased by 8.5% while the static and dynamitic performance maintain nearly unchanged.