Aiming at the problem of large inertia, poor motion control and low imaging efficiency of a widefield phase contrast Computed Tomography (CT) experimental device, the static and dynamic performance of the original casting turntable is analyzed by finite element method (FEM). The result as constraint, lightweight design for the CT turntable was conducted again based on welding structure. The topology optimization method was used to analyze the distribution of material inside turntable. Sandwich welding ribs were arranged reasonably according to the topology result. Mathematical model was established in OptiStruct, in which part thickness as design variable, sensitivity of the thickness to total mass, static stiffness and first modal frequency was analyzed. Finally, parts thickness is rematched, and the optimized turntables mass is reduced by 576% with respect to the original.