This　paper　proposed　a　new　four-degree-of-freedom　dynamic　model　of　the　bearing-rotor　system　based　on　ball　bearing　without　Raceway　Control　Hypothesis,　and　both　the　inertia　forces　of　balls　and　the　tilting　motions　of　rotor　are　fully　considering　in　the　calculation　of　restoring　forces　and　moments　of　ball　bearings.　Then　the　dynamic　model　are　solved　by　the　fourth-step　Runge-Kutta　method,　and　the　dynamic　responses　of　rotor　system　including　the　displacement,　velocity　and　center　orbits　are　obtained,　and　the　influences　of　rotating　speeds,　eccentricity　and　symmetry　of　rotor　are　studied　and　analyzed.　The　results　show　that　both　the　varying　compliance　of　ball　bearing　and　rotor　eccentric　force　have　a　great　influence　on　the　dynamic　responses　and　motion　patterns　of　bearing-rotor　system,　and　the　titling　motion　of　bearing-rotor　should　be　considered　in　the　analysis　of　asymmetric　rotor　or　the　symmetric　rotor　under　some　specific　conditions.　Copyright　©　2019　ASME.