In　order　to　study　the　seismic　performance　of　the　staircase　in　the　cast-in-place　reinforced　concrete　frame,　a　1/2　scaled　specimen　of　the　structural　unit　composed　of　concrete　frame　and　staircase　was　tested　quasi-statically.　The　test　demonstrated　the　failure　mode　and　mechanism　of　the　structural　unit　as　a　whole　and　those　of　its　various　components,　and　the　load-carrying　capacity,　displacements　and　other　aspects　related　to　seismic　behavior　were　also　measured.　The　test　shows　that,　when　fully　connected　to　the　main　structure　with　the　conventional　manner　of　construction,　the　staircase　works　as　asymmetrically　inclined　bracings　in　the　structure,　resulting　in　its　early　cracking　and　fast　damaging,　and　consequently,　its　functions,　such　as　seismic　rescue　and　evacuation,　could　not　be　ensured;　meanwhile,　it　also　causes　irregular　forces　of　the　frame　members,　leading　to　the　brittle　failure　of　the　column　in　one　side　of　frame　and　then　the　complete　failure　of　the　specimen.　The　enclosed　area　of　hysteretic　loop　of　the　specimen　is　relatively　small　and　its　peak　value　of　load　reaches　high　but,　after　that,　the　capacity　decreases　fast.　The　rigid　connection　between　the　frame　column　and　the　supporting　beam　of　the　stair　platform　on　the　half　story　makes　some　frame　columns,　which　are　already　in　complex　state　of　loading,　the　short　columns,　leading　to　the　local　collapse　of　such　column　and　failure　in　other　parts　of　the　frame　suddenly.　Therefore,　the　staircase　connected　to　the　concrete　frame　with　such　a　conventional　manner　as　mentioned　above　is　adverse　to　seismic　resistance　of　the　structure.　©,　2014,　Science　Press.　All　right　reserved.