Contact　characteristics　of　bolt　connection　contact　surface　are　the　key　to　affect　dynamic　and　static　characteristics　of　mechanical　system.　When　a　contact　surface　is　in　vibration　fatigue　state,　it　can　cause　increase　in　damping　and　decrease　in　resonance　frequency.　Therefore,　establishing　an　accurate　contact　model　of　bolted　contact　surface　is　of　great　significance　to　study　dynamic　characteristics　of　the　whole　machine　tool.　Here,　combined　with　the　plastic　index　expression,　statistical　roughness　parameters　and　fractal　parameters　given　by　Greenwood　and　Williamson,　a　plastic　index　model　related　to　frequency　ordinal　number　of　micro-convex　body　was　established.　According　to　the　plastic　index,　the　critical　frequency　ordinal　number　of　elastic-elastoplastic-plastic　deformation　of　micro-convex　body　was　obtained.　Based　on　Hertz　contact　theory,　the　contact　load　and　contact　stiffness　of　the　whole　contact　surface　were　obtained　through　integrating　the　micro-convex　body　within　different　frequency　intervals.　Finally,　the　correctness　of　the　theoretical　model　was　verified　through　the　combination　of　finite　element　simulation　and　tests.　It　was　shown　that　the　theoretical　model　described　above　has　stronger　engineering　application　value.　©　2022,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.