Ultra-high-performance　concrete　(UHPC)　has　advantages　in　mechanical　properties　and　bond　properties,　which　was　available　to　connect　the　precast　members　of　prefabricated　composite　structures.　In　this　paper,　some　kinds　of　wet　connections　with　post-cast　UHPC　applied　in　the　composite　beam　with　prefabricated　components　(slab　and　steel　beam)　were　designed,　and　the　longitudinal　force-slip　behaviors　for　the　above　UHPC　connections　were　investigated　through　a　series　of　push-out　tests.　In　the　case　of　the　specimens　with　the　post-cast　UHPC　rectangular　connection,　which　failed　in　the　interface　between　the　precast　slab　and　UHPC　connection　instead　of　the　concrete　region　around　the　stud　connectors,　the　increase　in　interface　reinforcement　ratio　was　beneficial　for　enhancing　the　interface　shear　resistance.　The　arrangement　of　two　layers　of　steel　bars　out　of　the　precast　slab　side　could　make　full　use　of　the　plastic　properties　of　bottom　interface　reinforcements　to　strengthen　the　ultimate　shear　strength　and　ductility　of　the　interface.　Compared　with　the　rectangular　connection,　the　post-cast　UHPC　connection　with　Tsection　presented　a　better　interface　performance　by　increasing　the　bond　area,　while　the　increase　of　the　transverse　width　only　worked　in　a　limited　range　due　to　the　interface　shear　lag　effect.　Based　on　the　experimental　and　theoretical　analyses,　the　formulas　corresponding　to　different　types　of　post-cast　UHPC　connections　in　prefabricated　composite　beams　were　proposed　to　calculate　the　longitudinal　shear　capacity,　then　the　composition　of　equations　and　the　reduction　factors　corresponding　to　different　conditions　were　recommended.