In　order　to　improve　resisting　performance　of　heat,　wear　and　erosion　as　well　as　anti-thermal　fatigue,　surface　build-up　welding　material　of　brake-disc　for　drilling　rig　with　better　performance　is　developed,　and　its　wear　mechanism　is　investigated　based　on　friction　and　wear　experiment　at　variable　temperature.　Morphology,　constituents　and　phase　structure　of　wear　surface　of　brake　disc　are　analyzed　by　employing　SEM,　EDAX　and　XRD　when　thermal　equilibrium　temperature　is　at　150　degrees　C　and　300　degrees　C,　and　its　tribological　behaviour　and　wear　mechanism　of　surface　build-up　welding　materials　are　revealed.　In　initial　stage　of　wear,　friction　temperature　is　lower　and　hard　particles　like　AL(2)O(3),　SiO2,　SiC,　TiO　in　brake　block　plough　the　surface　of　brake-disc,　oxide　layer　forms　on　friction　surface　with　rise　of　friction　temperature　and　its　cracking　and　regenerating　become　a　major　way　of　wear,　meanwhile　hard　grains　in　brake　block　slough　off　due　to　frequent　ploughing　and　three-body　abrasive　wear　occurs,　and　spalling　of　surface　film　is　mainly　caused　by　fatigue.　In　stage　of　high　temperature　wear,　oxidization　wear　and　plastic　deformation　of　brake-disc　increase　greatly,　brake-block　starts　to　soften,　severe　adhesive　wear　occurs　and　spalling　of　surface　film　is　mainly　caused　by　adhesive　tearing.　Wear　mechanism　of　brake-disc　is　comprehensive　effects　of　abrasive,　oxidizing　and　adhesive　wear.