This　paper　deduced　the　equation　of　motion　for　non-affixation　of　spring,　right　affixation　of　spring　and　left　affixation　of　spring　on　the　basis　of　the　multi-particle　structural　analytic　model,　and　developed　the　computer　program　to　prevent　the　failure　of　rubber　bearing　under　low-frequency　excitation.　A　shaking　table　test　of　a　five-floor　steel-frame　model　was　completed　successfully　in　Beijing　University　of　Technology.　The　results　showed　that　the　variable　stiffness　isolated　protection　device　can　effectively　reduce　the　horizontal　deformation　to　prescribed　limits,　prevent　the　rubber　bearings　from　failure　because　the　dynamic　character　of　the　structure　has　been　changed,　and　make　the　interlayer　shear　forces　in　the　super-structure　increase　slightly.