According　to　the　real　dimension　of　the　braking　disc　and　the　pads,　the　modeling　for　three-dimensional　transient　thermal-structure　coupling　during　the　emergency　braking　is　established　based　on　the　effect　of　the　moving　heat　source　with　relative　sliding　variation　and　the　coupling　of　the　frictional　thermal　flow　between　the　disc　and　the　pad.　By　using　the　nonlinear　multiphysics　field　of　the　ANSYS　software,　the　braking　process　of　the　disc　brake　is　simulated.　The　distribution　of　the　temperature　and　the　stress　of　the　disc　during　the　braking　are　analyzed.　The　temperature　and　the　stress　are　coupled.　During　the　braking,　the　transient　temperature/stress　variation　present　periodical　fluctuations　due　to　the　entering　heat　flux　and　the　thermal　convection　alternately.　The　variational　period　of　the　temperature/stress　increases　with　the　braking　time　prolonged.　And　the　reason　of　radial　thermal　fatigue　fracture　of　the　disc　is　discussed.