Accurate　modeling　of　contact　stiffness　is　crucial　in　predicting　the　dynamic　behavior　and　chatter　vibration　of　spindle-toolholder　system　for　high-speed　machining　centers.　This　paper　presents　a　fractal　theory-based　contact　model　of　spindle-toolholder　joint　to　obtain　the　contact　stiffness　and　its　real　contact　area.　Topography　of　the　contact　surfaces　of　spindle-toolholder　joint　is　fractal　featured　and　determined　by　fractal　parameters.　Asperities　in　micro-scale　are　considered　as　elastic　or　plastic　deformation.　Then,　the　contact　stiffness,　the　real　contact　area,　the　elastic　contact　force,　and　the　plastic　contact　force　of　the　whole　contact　surface　are　calculated　by　integrating　the　micro　asperities.　The　relationship　of　the　contact　stiffness　and　the　drawbar　force　follows　a　power　law,　in　which　the　power　index　is　determined　by　the　fractal　parameters.　Experiments　are　conducted　to　verify　the　efficiency　of　the　proposed　model.　The　results　from　the　fractal　contact　model　of　spindle-toolholder　joint　have　good　agreement　with　those　of　experiments.