Plate　stiffened　with　U-ribs　of　hybrid　steel　types　is　designed　to　adopt　different　strength　steel　materials　for　steel　plate　and　the　stiffening　U-ribs　according　to　their　different　forces,　which　may　make　full　use　of　the　materials　and　reduce　the　project　cost.　Nine　specimens　of　plates　stiffened　with　U-ribs　of　hybrid　steel　types　were　designed　and　manufactured,　taking　the　structure　size　and　material　strength　of　the　steel　plate　and　the　stiffening　U-ribs　as　the　design　variables.　Experiments　of　the　specimens　under　axial　loads　were　carried　out.　The　failure　mode,　stability　bearing　capacity　and　the　load-displacement　relationship　of　the　hybrid　steel　U-rib　stiffened　plate　were　investigated.　The　stability　mechanism　of　plate　stiffened　with　U-ribs　of　hybrid　steel　types　under　axial　load　was　investigated,　in　which　the　members　with　low　strength　is　equivalent　to　members　with　high　strength　by　adding　initial　stress,　and　the　distribution　of　the　weld　residual　stress　is　also　considered.　Test　results　show　that　there　are　two　kinds　of　failure　modes,　i.　e.,　buckling　as　a　whole　and　local　buckling　or　strength　yielding.　For　the　failure　of　buckling　as　a　whole,　the　deflection　direction　may　be　toward　the　plate　or　the　U-rib,　while　the　local　buckling　or　strength　yielding　may　occur　in　the　flange,　web　of　the　U-rib　or　the　stiffened　plate.　Whether　the　rotation　of　the　two　ends　of　the　specimen　is　restrained　or　not　has　a　great　influence　on　the　test　results.　When　the　rotation　is　restrained,　the　U-rib　near　the　end　of　the　specimen　will　locally　buckle.　If　the　rotation　is　not　restrained,　the　U-rib　in　the　middle　height　of　specimen　will　locally　buckle　or　the　specimen　as　a　whole　will　fail　due　to　bending.　For　the　specimen　buckling　as　a　whole,　the　specimen　exhibits　a　good　ductility　and　the　average　peak　stress　will　change　quite　a　lot　among　various　specimens;　for　the　specimens　that　fail　by　local　buckling　or　strength　yielding,　behave　brittle　and　the　average　peak　stresses　are　almost　the　same　for　all　specimens.　©　2016,　Editorial　Office　of　Journal　of　Building　Structures.　All　right　reserved.