Supported　alloy　catalysts　have　been　extensively　applied　to　many　significant　industrial　chemical　processes　due　to　the　abundant　active　sites　with　distinguishable　geometry　and　electron　states.　However,　a　detailed　in　situ　investigation　of　the　interaction　between　support　and　alloy　nanoparticles　is　still　lacking.　Here,　a　subversive　＇tearing　effect＇　on　the　interface　of　TiO2-supported　NiRu　alloy　nanoparticles　is　in　situ　discovered　by　environmental　transmission　electron　microscopy　(ETEM)　with　a　dramatic　redispersion　process　of　alloy　nanoparticles　from　similar　to　25　nm　to　2-3　nm　under　the　repeated　hydrogen　reduction.　Dual-driven　by　the　distinct　alloy-support　interaction　involving　the　restructuring　of　alloy　nanoparticles　and　growth　of　TiOx　overlayer,　larger　NiRu　alloy　nanoparticles　spontaneously　disintegrate　into　atoms　migrating　on　support.　Atoms　are　finally　captured　by　the　defects　generated　on　TiO2　during　the　repeat　reduction,　which　also　confines　the　further　growth　of　the　newly　alloy　nanoparticles.　Owing　to　this　specific　alloy-support　interaction,　smaller　alloy　nanoparticles　on　TiO2　support　are　much　more　stable　than　the　bigger　ones,　which　holds　promise　for　industrial　applications　as　durable　catalysts.　This　novel　metal-support　interaction　with　the　＇tearing　effect＇　revealed　on　supported　alloy　catalysts　provides　new　knowledge　on　the　structure-performance　relationships　in　all　the　alloy　catalysts　for　hydrogenation　reactions.