The radiation damping of the elastic half-space significantly affects the modal damping ratio of the superstructure. However, conventionally, it is hard for the traditional shaking table test to exhibit the radiation damping effect of the site due to the boundary effects of the model box. In this paper, a new impulsive-force-based real-time dynamic hybrid testing (RTDHT) method is developed to investigate the soil-structure interaction (SSI) effect on the structural dynamic characteristics. In the new method, the superstructure is considered to be a physical substructure and the semi-infinite soil deposits is as assumed to be a numerical substructure. The free vibration of the superstructure in the SSI system is excited by applying impulsive force at the interface of the soil and superstructure. Then, a time-domain method combining empirical wavelet transform and Hilbert transform is developed to identify structural modal parameters, which significantly improves the efficiency and accuracy of the experimental modal analysis for the shaking table test of the SSI system. A series of the RTDHT of a two-story steel frame structure on elastic half-space site is carried out, which validated the effectiveness and accuracy of the test method by comparisons between the experimental and numerical results.