Graphene　quantum　dots　(GQDs)　prepared　by　the　top-down　route　have　promising　applications　in　chemical　sensing　and　biosensing　for　their　easy　preparation,　strong　electrochemiluminescence　(ECL),　low　cytotoxicity,　easy　labeling,　and　favorable　biocompatibility.　However,　the　extraordinary　water　solubility　of　GQDs　results　in　poor　immobilization　of　GQDs　on　the　sensing　interfaces　and　then　low　sensing　sensitivity　and　stability,　which　limit　their　extensive　sensing　applications.　In　order　to　solve　the　problem　of　poor　immobilization　of　GQDs　on　the　sensing　interfaces　and　improve　their　sensing　performances,　we　in　situ　prepared　and　loaded　single-layered　GQDs　onto　multiwalled　carbon　nanorings　(MWCNRs)　by　a　simple　one-step　acid　treatment　of　raw　single-walled　carbon　nanotubes　(SWCNTs)　with　side　products　of　MWCNRs.　It　is　for　the　first　time　that　a　large　number　of　MWCNRs　with　well　crystallization　nanostructures,　good　electroconductivity,　and　excellent　chemical　stability　were　found　in　raw　SWCNTs　and　applied　for　ECL　sensing.　During　the　HNO3-treatment　of　the　raw　SWCNTs　(nanohybrids　of　SWCNTs/MWCNRs),　the　component　of　SWCNT　was　oxidized　into　single-layered　GQDs,　while　the　component　of　MWCNR　was　essentially　kept　unchanged.　The　resultant　GQDs　were　in　situ　and　stably　immobilized　on　the　surfaces　of　MWCNRs　by　acid-enhanced　π−π　stacking　interactions,　in　the　absence　of　electrostatic　repulsion.　The　synthesized　MWCNRs@GQDs　exhibit　a　strong　and　stable　ECL　activity　on　the　sensing　interface　and　show　promising　applications　in　ECL　immunoassay　of　biomarkers,　such　as　human　chorionic　gonadotropin.　©　2025　American　Chemical　Society.