Attempt is made to solve some of the existing problems due to the application of themodal control method. A wave control method--the method of successive decrease is set up at first, which isaimed at one harmonic wave. Then, a new design method in wave control is proposed based on the above method. The problem of control spillover is analyzed and the concept of harmonic wave filter is introduced.As an example, the problem of the control of structures with closely spaced natural frequencies is treated by both the method of modal control and the method of successive decrease. The numerical results show that the method of successive decrease is more effective than the method of modal control for this problem. Attempt is made to solve some of the existing problems due to the application of themodal control method. A wave control method - the method of successive decrease is set up at first, which isaimed at one harmonic wave. Then, a new design method in The problem of control spillover is analyzed and the concept of harmonic wave filter is introduced. As a example, the problem of the control of structures with closely spaced natural frequencies is treated by both of the method of modal control and the method of successive decrease. The numerical results show that the method of successive decrease is more effective than the method of modal control for this problem.