High-strength　bolted　connections　have　attracted　increasing　attention　over　the　past　few　decades　because　they　can　safely　transfer　the　design　load.　However,　the　effect　of　the　preload　loss　on　the　mechanical　behavior　of　the　bolted　connections　has　not　been　investigated　sufficiently,　This　paper　presents　an　experimental　investigation　of　the　bearing　capacity　of　high-strength　bolted　connections　with　loose　bolts　(lacking　pretension　force).　The　tests　investigated　ninety　specimens　with　loose　bolts　and　six　specimens　without　loose　bolts　for　comparison.　The　results　showed　that　bolt　fracture　was　the　only　failure　mode　for　all　of　the　tested　connections　under　uniaxial　tension.　The　global　behavior　of　the　tested　connections　exhibited　four　stages,　and　the　features　of　each　stage　were　summarized.　The　connections　with　different　tightening　conditions　exhibited　a　similar　trend　in　terms　of　strain　development　around　the　bolt　holes.　The　effect　of　the　slip　coefficient,　position　and　number　of　loose　bolts,　and　the　plate　thickness　is　elucidated　through　parametric　studies.　It　is　found　that　the　yield　load　of　high-strength　bolted　connections　may　be　affected　by　the　pretension　force　and　the　slip　coefficient,　while　the　effect　of　the　slip　coefficient　gradually　decreases　with　the　increasing　number　of　loose　bolts.　The　experimental　results　are　compared　to　the　calculated　ultimate　bearing　resistance　according　to　the　GB　50017,　Eurocode　3,　and　AISC　360-16　standards.　It　is　found　that　the　resistance　prediction　of　the　standards　may　be　too　conservative　for　the　prediction　of　the　ultimate　bearing　capacity　of　loose　high-strength　bolted　connections　when　bolt　fracture　governs　failure.　Practical　design　recommendations　in　the　algebraic　form　are　presented　and　verified　to　predict　the　yield　load　and　ultimate　bearing　capacity　of　loose　high-strength　bolted　connections.