An　experiment　of　three　T-shape　beam-column　steel　joints　with　intensive　cover　plate　was　conducted　under　low　cyclic　loading　with　different　cycle　numbers,　to　study　seismic　performance　of　the　joints　subjected　to　long-period　ground　motions.　Effects　of　cycle　number　on　mechanical　performance　and　length　of　plastic　hinge　were　analyzed.　The　results　show　that　as　the　cycle　number　increases,　capacity　of　the　joint　decreases,　and　plastic　hinge　of　the　joint　develops　longer　which　appears　closer　to　the　cover　plate,　and　the　platform　of　skeleton　curve　grows　longer,　and　the　stiffness　attenuates　slightly.