Methods　utilising　rigid　preloading　and　constant　preloading　in　ball　bearing　systems　may　not　be　adequate　to　address　the　optimisation　of　problems　in　which　preloading　occurs.　This　is　because　of　non-uniform　loading　on　the　bearings　that　is　induced　by　manufacturing　error,　assembly　error　and　external　loads.　A　non-uniform　preload　is　presented　for　the　analysis　of　non-uniform　bearing　loading.　A　simulation　method　is　developed　to　determine　the　effects　on　non-uniform　loading　on　bearing　thermal　performance　under　different　preloads.　A　three-degree-of-freedom　model　is　built　to　simulate　the　heat　generation　rate　of　angular　contact　ball　bearings　under　non-uniform　preloads.　In　this　model,　the　non-uniform　preload　is　divided　equally　into　two　parts:　a　uniform　preload　and　an　equivalent　moment.　The　bearing　heat　generation　rate　can　then　be　employed　in　finite　element　analysis　software　to　simulate　the　temperature　field　associated　with　the　entire　ball　bearing.　The　simulation　data　shows　that　non-uniform　preloading　conditions　on　ball　bearings　can　decrease　heat　generation.　The　results　also　show　that　non-uniform　preloads　can　alleviate　heating　concentrations　and　reduce　peak　temperature　values　under　working　conditions.