A　radial　shaft　seal　(RSS)　model　is　established　to　reveal　mixed　thermal　lubrication　(MTL)　and　wear　performance　at　speeds　ranging　from　3000　r/min　to　7000　r/min.　The　model　takes　into　account　the　initial　temperatures　of　the　oil　medium　and　the　running　time　of　the　RSS　to　investigate　the　transition　limit　of　lubrication.　Then　a　thermal　fluidsolid　method　was　developed　to　simulate　the　lubrication　performance　of　RSS,　which　shows　lubrication　transition　boundaries　through　rough　micro　convex　bodies　for　wear　deformation.　The　RSS　deforms　wedge-shaped　during　the　wear　process　and　a　localized　fluid　pressure　is　created　on　the　convex　bodies.　Considering　the　wear　deformation　of　the　convex　bodies　due　to　the　wedge　effect,　the　micro　performance　of　the　RSS　can　fully　describe　the　mechanism　of　the　leakage　rate.　As　the　dynamic　pressure　decreases　and　the　leakage　rate　increases　with　the　temperature　of　the　medium,　the　RSS　lubrication　gradually　transitions　from　MTL　to　EHL.　Thus,　the　initial　medium　temperature　should　be　considered　to　maintain　the　RSS　under　the　mixed　lubrication　regime　with　low　friction.