This　paper　develops　a　three-dimensional　(3D)　thermal-structure　coupling　model,　implements　transient　stress　analysis　of　thermoelastic　contact　of　disk　brakes　with　a　frictional　heat　variation　and　identifies　the　source　of　the　thermal　fatigue.　This　thermostructure　model　allows　the　analysis　of　the　effects　of　the　moving　heat　source　(the　pad)　with　a　variable　speed　and　integrates　the　heat　flux　coupling　between　the　sliding　surfaces.　To　obtain　the　transient　stress/temperature　fields　of　the　brake　under　an　emergency　braking,　the　thermoelastic　problem　under　this　3D　model　is　solved　by　the　finite　element　method.　The　numerical　results　from　the　analysis　and　simulation　show　the　temperature/stress　of　the　disk　presenting　periodic　sharp　fluctuation　due　to　the　continuous　cyclic　loading;　its　varying　frequency　corresponds　to　the　rotated　cycle　times　of　the　braking　disk.　The　results　demonstrate　that　the　maximum　surface　equivalent　stress　may　exceed　the　material　yield　strength　during　an　emergency　braking,　which　may　cause　a　plastic　damage　accumulation　in　a　brake　disk,　while　a　residual　tensile　hoop　stress　is　incurred　on　cooling.　These　results　are　validated　by　experimental　observation　results　available　in　the　literature.　Based　on　these　numerical　results,　some　suggestions　for　avoiding　fatigue　fracture　propagation　are　further　presented.　Copyright　©　2007　by　ASME.