Bolted　connections　are　preferred　in　prefabricated　steel　structures　because　of　the　convenience　for　construction　and　quality　control.　A　prefabricated　steel　structural　system　with　truss　beams　and　bolted　joints　were　proposed,　and　enlarged　bolt　holes　were　adopted　in　the　joints　for　easier　assembly　and　better　energy　dissipations.　A　series　of　6　truss-to-column　joint　specimens,　with　oversized　or　slotted　bolt　holes,　were　tested　under　cyclic　loads.　The　resistance,　the　hysteresis　behaviour,　the　ductility,　the　energy　dissipation　capacity,　and　the　slipping　behaviour　of　the　tested　joints　were　analysed,　and　the　influences　of　the　bolt　hole　dimensions　and　shapes　were　evaluated.　Finite　element　models　were　established　and　validated　for　further　investigation　of　the　joint　performances.　According　to　the　results,　the　enlarged　bolt　holes　would　slightly　decrease　the　slipping　resistance,　but　would　significantly　improve　the　joint　ductility　and　energy　dissipation　capacity.　The　slippages　in　the　joints　with　oversized　or　slotted　bolt　holes　could　make　38%-59%　of　the　contributions　to　the　energy　dissipation　capacity,　proving　that　the　slippages　could　be　utilized　in　seismic　design.　Based　on　the　investigations,　the　diameters　of　the　oversized　bolt　holes　are　recommended　to　be　4　mm　larger　than　the　nominal　bolt　diameter,　and　a　0.3　mm-thick　copper　plate　is　recommended　to　be　adopted　between　the　connected　plates　to　obtain　stable　slip　behaviours.　Simplified　calculation　methods　for　the　slipping　resistance　and　the　yield　resistance　of　the　investigated　joints　were　proposed　and　evaluated　to　have　acceptable　accuracy　for　resistance　prediction　and　design.