Dynamic　characteristics　between　the　cable-stayed　bridge　and　the　approach-bridge　are　different.　It　the　out-of-phase　vibrations　may　happen　under　horizontal　earthquake　effect.　Then　lead　to　collision　response,　cause　expansion　joint　damage　and　beam　collapse.　Aiming　at　the　research　on　the　collision　problem　between　the　big　span　cable-stayed　bridge　and　approach　span　is　not　overall　deeply,　the　anti-collision　measures　study　between　cable-stayed　bridge　and　approach　span　is　not　systematical　enough,　The　unseating　prevention　devices　shock　absorption　effect　on　the　collision　of　cable-stayed　bridge　and　approach　span　is　researched,　the　influence　law　of　unseating　prevention　devices　on　the　collision　of　cable-stayed　bridge　and　approach　span　is　analyzed　systematically.　The　results　show　that　unseating　prevention　devices　can　reduce　the　relative　displacement　of　adjacent　beams　and　collision　force　peak.　Unseating　prevention　devices　are　perfect　prevent　collision　measure　between　cable-stayed　bridge　and　approach　span,　But　the　influence　of　approach　span＇s　displacement　and　approach　span　fixed　pier　seismic　requirements　are　rather　complex.