To　study　the　dynamic　properties　and　failure　characteristics　of　karst　cave　roof　under　combined　action　of　pile　load　and　earthquake,　supported　by　the　pile　foundation　project　of　the　Zhoujiawan　Bridge　of　the　Chongqing-Guizhou　Railway,　the　main　control　parameters　of　rock　materials,　model　piles,　and　seismic　waves　were　determined　based　on　the　separation　similarity　method.　Through　19　groups　of　mixture　ratio　tests,　the　index　of　the　similar　material　ratios　of　rock　masses　used　in　shaking　table　tests　were　obtained,　and　the　small-scale　shaking　table　model　tests　of　karst　pile　foundation　were　conducted　considering　the　influence　of　different　thicknesses　of　the　roof　and　diameters　of　the　cave.　The　results　showed　that　the　existence　of　caves　changed　the　local　fundamental　frequency　and　dynamic　characteristics　of　the　model,　and　it　hindered　the　transmission　of　seismic　waves　and　dissipated　energy.　The　frequency　spectrum　of　the　wave　had　no　direct　relation　with　the　size　of　the　upper　load.　The　cracks　in　the　pile-end　caused　by　the　combined　action　of　the　pile-end　load　and　the　earthquake　gave　rise　to　the　overall　amplitude　decrease　of　the　seismic　waves,　which　caused　the　change　of　the　fundamental　frequency　of　the　model.　The　internal　cracks　in　the　model　increased　with　the　enhancement　of　the　acceleration　of　the　seismic　waves,　resulting　in　a　progressive　increase　in　the　damping　ratio,　which　caused　the　main　frequency　of　the　vibration　to　decrease.　Variation　of　the　same　kind　of　seismic　wave　only　altered　the　wave　amplitude,　while　different　kinds　of　seismic　waves　led　to　the　distribution　changes　of　the　fundamental　frequency.　The　strain　of　the　monitoring　point　increased　with　the　increment　of　the　peak　of　the　seismic　waves.　Shearing　failure　of　the　karst　roof　occurred　when　the　diameter　of　the　cave　was　small,　but　punching-shearing　failure　happened　when　the　diameter　was　larger.　©　2019,　Editorial　Board　of　Journal　of　Harbin　Institute　of　Technology.　All　right　reserved.