In　view　of　thermal　resistance　problem　of　the　motorized　spindle　system,　this　paper　proposes　a　thermal　resistance　network　model　of　spindle-bearing-bearing　pedestal　based　on　the　fractal　and　Hertz　contact　theory.　According　to　this　model　and　Kirchhoff＇s　law,　the　heat　balance　equations　for　thermal　nodes　are　established　and　solved　with　Gauss-Seidel　iterative　method　to　gain　temperature　values　of　the　main　thermal　nodes.　In　order　to　accurately　understand　thermal　characteristics　of　the　motorized　spindle　system,　the　effect　of　thermal　contact　resistance　and　thermal-conduction　resistance　is　taken　into　consideration.　Thermal　simulation　analysis　is　carried　out　on　the　motorized　spindle　system.　On　a　precision　horizontal　machining　center,　the　temperature　rise　of　motorized　spindle　parts　is　implemented　under　different　rotational　speeds　with　LMS　data　acquisition　system.　It　is　shown　that　temperature　values　based　on　thermal　resistance　network　model　agree　well　with　those　of　simulation　analysis　and　experimental　results.　What　is　more,　the　whole　thermal　deformations　of　the　main　components　of　the　motorized　spindle　system　are　analyzed.