Headed　stud　connectors　play　a　key　role　in　steel-ultra-high　performance　concrete　(UHPC)　composite　slab,　which　has　many　applications　in　long-span　bridges.　In　this　paper,　a　finite　element　(FE)　model　is　validated　by　a　series　of　push-out　tests　to　study　the　shear　behaviors　of　headed　stud　in　steel-UHPC　composite　slab.　After　validation,　the　interaction　between　stud　and　UHPC　is　explored　and　parametric　analysis　is　performed.　The　influence　of　weld　collar,　diameter　and　spacing　of　stud　on　the　failure　mode,　shear　bearing　capacity　and　load-slip　relationship　of　stud　connector　are　discussed.　From　FE　results,　the　group　stud　effect　should　be　considered,　as　the　ratio　of　stud　spacing　to　diameter　is　less　than　3.5,　5.0　and　6.5　for　the　diameter　of　13　mm,　16　mm　and　19　mm　respectively.　A　formula　to　predict　the　shear　bearing　capacity　of　stud　is　proposed　by　considering　the　influence　of　weld　collar　and　group　stud　effect.　A　shear-slip　model　of　stud　is　established　based　on　experimental　and　FE　analysis　results.