The　contact　mechanism　of　bolted-joint　interface　in　elastic-plastic　deformation　regime　is　difficult　to　determine.　Acrooding　to　the　contact　mechanics　and　the　assumption　that　the　transition　from　elastic　to　fully　plastic　deformation　of　a　contacting　asperity　is　continuous　and　smooth,　the　new　polynomial　function　is　constructed　to　describe　the　relationship　between　contact　deformation　and　real　contact　area　in　elastic-plastic　contact　regime.　The　real　area　of　contact,　contact　load　and　contact　stiffness　model　are　developed　based　on　statistical　method.　Theoretical　calcutaion　results　show　that　contact　load,　real　contact　area　and　contact　stiffness　increases　as　the　mean　surface　separation　decrease.　The　real　contact　area　and　contact　stiffness　increases　with　the　increases　of　the　contact　load,　especially,　the　value　of　contact　stiffness　and　real　contact　area　approached　to　ideal　contact　stiffness　and　nominal　contact　area　when　the　contact　load　increases　to　a　certain　extent,　respectively.　The　real　contact　area　increases　as　plasticity　indices　increases,　and　mean　surface　separation　and　contact　stiffness　decrease　in　the　elastic　and　elastoplastic　deformation　regime.　The　mean　surface　separation　and　contact　stiffness　increases　as　plasticity　indices　increases,　and　real　contact　area　decreases　in　the　fully　plastic　deformation　regime.　©　2016　Journal　of　Mechanical　Engineering.