Abstract: Based on the elasticity similitude law,three scaled models,including a frame structure with rigid foundation(RF),soil-structure interaction(SSI) with only one structure and structure-soil-structure interaction(SSSI),were constructed to investigate the effects of neighborhood structures on the dynamic characteristics of the soil-structure system. Then,the impulse excitation method was used to identify the frequencies,mode shapes,and damping ratios of the three models. All of the identified parameters were compared with those of prototypes by the finite element method. Test and numerical results show that there are two natural modes of SSSI,whose frequencies are close but phases are opposite corresponding to each mode of SSI. Moreover,the natural frequency of SSI will be in the interval of the corresponding two frequencies of SSSI. The vertical and rocking displacements increase in the SSSI system due to the effects of neighborhood structures. The scale factors of frequencies between prototypes and models agree with the similitude law.