The　machine　tools　are　consisted　of　many　parts　and　most　of　them　are　connected　by　the　bolts.　Accurate　modeling　of　contact　stiffness　and　damping　for　bolted　joint　is　crucial　in　predicting　the　dynamic　performance　of　machine　tools.　This　paper　presents　a　modified　three-dimensional　fractal　contact　model　to　obtain　the　stiffness　and　damping　of　bolted　joint.　Topography　of　the　contact　surface　of　bolted　joint　is　fractal　featured　and　determined　by　fractal　parameters.　Asperities　in　microscale　are　considered　as　elastic,　elastic-plastic,　and　full　plastic　deformation.　The　expand　coefficient　is　introduced　to　the　size-distribution　function　of　asperities.　The　real　contact　area,　contact　stiffness,　and　damping　of　the　contact　surface　can　be　calculated　by　integrating　the　microasperities.　The　relationship　of　contact　stiffness,　damping,　fractal　dimension　D,　and　fractal　roughness　parameter　G　can　be　obtained.　Experiments　are　conducted　to　verify　the　efficiency　of　the　proposed　model.　The　results　show　that　the　theoretical　mode　shapes　are　in　good　agreement　with　the　experimental　mode　shapes.　The　relative　errors　between　the　theoretical　and　experimental　natural　frequencies　are　less　than　3.33%,　which　is　less　than　those　of　the　W-K　model　and　L-L　model.　The　presented　model　can　be　used　to　accurately　predict　the　dynamic　characteristic　of　bolted　assembly　in　the　machine　tools.