The　instantaneous　angular　speed　(IAS)　has　been　gradually　applied　to　bearing　fault　identification.　The　IAS　of　the　fault　bearing　have　periodic　disturbance　by　bearing　dynamic　modeling　and　fault　simulation　experiment　in　some　studies.　However,　few　of　them　has　involved　the　local　characteristics　of　IAS　periodic　disturbance,　especially　the　large　clearance　bearing,　which　may　lead　to　misdiagnosis.　In　this　paper,　a　bearing　rolling　element　fault　dynamic　model　is　proposed　by　considering　the　contact　stiffness　between　the　rolling　elements　and　races　based　on　the　Hertzian　contact　theory.　Moreover,　A　fault　with　0.25　mm　width　and　0.2　mm　depth　was　seeded　on　the　roller　of　the　bearing　using　the　laser　to　verify　the　validity　of　simulation　results.　The　results　show　that　the　periodic　impulse　is　observed　in　the　IAS,　which　is　mainly　due　to　the　sudden　change　of　torque　when　the　defect　of　the　rolling　element　contacts　the　raceway,　especially　in　the　load　area.　©　2022　IET　Conference　Proceedings.　All　rights　reserved.