The　bearing　stiffness　model　is　established　based　on　the　Hertz　contact　theory　and　the　hydrodynamic　lubrication　theory　of　rolling　bearing　in　this　paper,　the　dynamic　characteristics　of　the　angular　contact　ball　bearing　and　the　relationship　between　the　bearing　preload,　the　speed　and　the　stiffness　of　the　angular　contact　ball　bearing　is　analyzed,　as　well　as　the　influence　of　the　oil　film　stiffness　on　the　bearing　total　stiffness.　The　results　from　taking　71924ACD/P4A　bearing　as　an　example　shows　that　the　preload　and　the　speed　have　important　effect　on　the　stiffness　of　bearing.　By　the　contrast　of　two　kinds　of　situations,　a　conclusion　can　be　drawn　that　when　considering　the　oil　film　stiffness,the　total　stiffness　reduces　0-40%　than　not　considering　the　oil　film　stiffness.