The　effects　of　different-temperature-heat　treatment　on　crack　healing　and　strength　of　TiCP/Al2O3　and　SiCW-Al2O3　composites　were　studied　systematically.　The　results　show　that　when　the　samples　are　heat-treated　at　1000　similar　to　1400　degreesC,　crack　healing　will　happen　and　the　strength　will　be　improved　largely.　The　diffusion　and　the　chemical　reactions　are　the　main　mechanism.　The　microstructure　and　thermal　physical　properties　of　the　surface　reactional　layer　determine　the　range　of　strength　improvement.　Stress　relaxation　is　benificial　for　strength,　but　the　oxidation-induced　bubbles　weaken　the　specimens.