A small base isolation system installed inside building is constructed for small structure. In order toinvestigate dynamic characteristics of this system by long period ground motion, excitation experiment andevaluation by numerical analysis is done. It is possible to reduce the response to 1/5, if input wave do not include afrequency component which is same as natural frequency of this system. Comparing response wave forms betweenexcitation experiment and numerical analysis modeling by single degree of freedom system, it is good agreement,although the peak amplitude between them indicates 10 % difference
