Abstract: The finite element model of frame structure for magnetic suspension control moment gyroscope (MS-CMG) was established and a modal analysis was implemented. On the view of the numerical results the optimization opinions of the frame structure were presented. The topology optimization module for continuum structure was developed and plugged in ANSYS via its APDL and UIDL combined with the bi-directional evolutionary structural optimization method (BESO). Thus the dynamic topological optimization of frame structure was realized with the fundamental frequency as constraint condition and the minimum weight as the target function. In this procedure, a nominal stress was presented and a relationship between the nominal stress and the corresponding mode shape of frame structure was established, by which the BESO was extended to apply in field of dynamic optimization. At last, a frame structure configuration was provided with optimum layout of stiffness and mass was given. Comparing with the initial configuration, the optimum frame structure satisfied the design demands and the fundamental frequency increased by 11.49%, whereas the mass decreased by 5.65%.