The　complicated　nonlinear　characteristic　of　structures　is　largely　responsible　for　bolted　joints.　In　traditional　structural　dynamical　analysis,　the　nonlinearity　of　the　joint　interfaces　is　ignored,　or　the　linear　method　is　used　to　model　for　bolted　joints,　which　causes　inaccurate　analysis　and　increases　the　difficulty　of　studying　nonlinear　dynamic　characteristics　for　bolted　joints.　The　energy　dissipation　mechanism　in　bolted　joints　occurs　as　a　result　of　micro-slip　motion　between　rough　surfaces　in　contact,　which　is　studied　by　experiment.　The　hysteresis　nonlinear　characteristic　of　bolted　joints　is　described　by　the　Iwan　model.　The　unknown　parameters　of　the　Iwan　model　are　deduced　by　unconstrained　nonlinear　optimization　and　the　Newton　iteration　method　under　quasi-static　harmonic　load,　and　the　hysteresis　nonlinear　characteristic　of　bolted　joints　with　the　change　in　harmonic　loading　can　be　obtained.　Finally,　the　experimental　and　numerical　simulation　results　are　compared　to　validate　the　Iwan　model.　The　results　show　that　the　Iwan　model　can　reflect　the　energy　dissipation　mechanism　and　the　hysteresis　nonlinear　characteristic　of　bolted　joints.