A　series　of　Cu45Zr42Al8Ag5　amorphous　rods　with　3　mm　in　diameter　were　prepared　by　isothermal　treatment　in　supercooled　liquid.　The　effect　of　isothermal　treatment　in　supercooled　liquid　on　the　thermal　stability　and　mechanical　properties　of　Cu-based　bulk　metallic　glasses　were　studied.　The　results　showed　that　the　samples　were　composites　containing　in　situ　crystalline　after　supercooling　treatment,　and　exhibited　an　excellent　thermal　stability.　From　the　compressive　stress-elongation　curves　of　Cu45Zr42Al8Ag5　BMG　alloys,　the　compressive　fracture　strength　gradually　decreased　with　the　increase　of　holding　time,　as　the　compressive　plastic　strain　increased.　And　the　best　compressive　strength　and　plastic　strain　were　2266　MPa　and　1.46%,　respectively.　Compared　to　the　samples　fabricated　by　overheating　treatment,　samples　prepared　by　supercooling　treatment　exhibited　better　mechanical　properties.　The　fracture　surface　of　the　sample　treated　at　1090　K　for　6　min　showed　obviously　vein-like　patterns,　which　was　contributed　to　the　high　compressive　fracture　strength　of　Cu-based　bulk　amorphous　alloys.