The　mechanical　behavior　of　spatial　TT-joints,　which　has　been　used　in　rectangular　hollow　section(RHS)　steel　tube　Vierendeel　truss　footbridge,　is　analyzed　using　FEA　in　this　paper.　The　results　show　that　location　of　maxium　Von-Mises　stress　are　in　the　corner　which　connects　vertical　member　to　chord;　but　for　the　spatial　TT-joints,　by　the　bending　moment　of　lateral　bracing,　location　of　maxium　Von-Mises　stress　transfers　to　the　chord　side　wall　connected　with　lateral　member.　Three　kinds　of　failure　modes　are　analyzed　as　follows:　the　local　buckling　failure　of　chord　side　wall　cennected　with　lateral　bracing＇s　bottom　flange,　the　crack　failure　mode　of　connection　weld　between　chord　and　lateral　bracing＇s　top　flange,　and　their　combined　failure　mode.　Under　the　actions　of　in-plane　bending　and　out-plane　bending,　the　moment　capacity　of　spatial　TT-joints　is　lower　than　the　resultant　moment,　it　can　not　be　calculated　by　in-plane　moment　or　out-plane　moment　formula,　and　their　interactions　should　be　considered.