To　get　the　load-bearing　behaviors　and　design　methods　of　a　modularized　prefabricated　steel　structure　with　lean-brace　joints,　the　finite　element　analysis　method　was　adopted,　the　restraints　effect　of　the　whole　structure　of　the　lean-brace　column　was　considered,　the　load-bearing　capacity　of　lean-brace　column　was　studied　in　the　integral　structure,　the　calculated　length　coefficient　of　the　column　was　conversely　derived　by　the　ultimate　load-bearing　capacity,　which　solved　the　key　problem　in　design　of　the　structure　system.　The　integral　finite　element　analysis　of　a　30-layer　structure　was　performed,　the　load-bearing　capacity,　the　failure　mode　and　failure　mechanism　of　the　new-type　structure　under　overload　horizontal　load,　overload　vertical　load　and　overload　were　obtained.　The　failure　mode　of　the　system　was　in　accordance　with　the　seismic　principle　of　“strong　column　weak　beam”.　Analysis　shows　that　the　structure　has　better　lateral　stiffness,　but　poorer　ductility.　It　is　reasonable　to　control　the　ultimate　load-bearing　capacity　coefficient　to　2.0　under　horizontal　load　and　vertical　load,　which　has　enough　safety　margin.　©,　2015,　Beijing　University　of　Technology.　All　right　reserved.