Topology optimization for constrained damping material in structures is investigated in order to suppress structural vibration through the optimal placement of constrained damping material in structure. A mathematical model to describe the topology optimization problem is established. In the topology optimization approach, structural modal damping ratio is designed as objection function, while constrained damping material consumption is considered as constraint condition. The sensitivity of modal damping ratio to the place is analyzed. An evolutionary criterion for placement of constrained damping material in a structure is presented. The formula of sensitivity is derived and used to determine the optimized placement of constrained damping material in structure. The topology optimization problem is further solved by evolutionary structural optimization (ESO) method. The numerical examples are given. The results show that a stable and dramatic increase of the modal damping ratio during the course of iterations can be observed. Therefore, an optimal layout of constrained damping material in structure is obtained. The comparison of amplitude frequency characteristics with the optimal and fully covered layout validates the effectiveness of proposed topology optimized approach.