The　bearing　temperature　of　a　high-speed　spindle　increases　with　its　speed.　This　restricts　the　rotational　velocity　and　precision　of　such　high-speed　spindles.　This　study　numerically　simulated　the　heat　generated　in　a　high-speed　spindle　bearings　at　different　rates　of　rotation.　Moreover,　the　model　distinguished　the　preload　methods,　rigid　preload　and　constant　preload.　The　geometrical　parameters　obtained　by　improving　Harris　bearing　model　and　the　heat　generation　are　calculated　by　Palmgren　theory.　The　study　shows　that　the　heat　generation　of　constant　preload　bearing　is　less　than　rigid　preload　bearing　in　a　spindle.　This　research　proposed　a　method　for　evaluating　the　heat　generation　quantificationally.