Lubricant　oil　is　crucial　to　the　rolling　bearings　as　the　main　medium　of　lubricating,cooling,cleaning,and　so　on.The　oil　starvation　in　and　around　the　contacts　is　harmful　to　the　performance　and　fatigue　life　of　rolling　bearings.Therefore,it　is　of　necessity　to　understand　the　behaviors　of　oil　transfer　and　the　patterns　of　air-oil　two-phase　flow　in　bearings,especially　with　the　influence　of　different　capillary　properties.This　work　established　a　transient　air-oil　two-phase　flow　model　in　a　ball　bearing　based　on　computational　fluid　dynamics(CFD).Groups　of　cases　are　implemented　to　investigate　the　behaviors　of　oil　transfer　and　air-oil　flow　under　different　capillary　conditions　with　speed,surface　tension,and　viscosity.Flow　patterns　are　classified　by　the　morphological　features　of　the　air-oil　flow.Staged　phenomena　are　analyzed　with　flow　patterns　and　reach　good　agreements　with　the　observations　from　experiments.It　is　found　that　the　oil　distribution　and　air-oil　flow　behaviors　in　a　ball　bearing　are　strongly　related　to　the　speed　and　the　ratio　of　oil　viscosity　and　air-oil　surface　tension(μoil/σ).The　flow　maps　imply　that　the　levels　of　capillary　number(Ca)may　be　the　boundaries　and　the　critical　points　of　flow　pattern　transition　between　the　different　flow　patterns　in　bearing.