Abstract: In this paper,the first four modal parameters of polymer filled steel tubes are determined with the application of the identification of performance parameters theory and the modal test method of hammer impact. And their proportional damping coefficients are determined by means of the method of least squares. The damping ratios of them are also determined with the test method of free vibration. By comparing with empty steel tubes, the results show that the damping ratios and the damping proportional coefficients of polymer filled steel tubes enhance remarkably,and they have very good damping properties.