A　novel　probe　for　the　highly　sensitive　detection　of　microRNA　with　enhanced　helix　accessibility　and　good　assembling　without　backfilling　was　developed　using　a　tripod　structure　fabricated　by　triplex　DNA.　A　layer　of　triplex　DNA　assembled　on　electrodeposited　reduced　graphene　oxide　was　used　as　the　capture　probe,　and　a　subsequent　hybridization　chain　reaction　that　promoted　the　efficient　intercalation　of　the　electrogenerated　chemiluminescence　(ECL)　emitter　[Ru-(bpy)(2),(dppz)](2+)　(bpy　refers　to　2,2＇-bipyridine,　and　dppz　refers　to　dipyrido[3,2-a:2＇,3＇-c]phenazine)　was　used　as　an　analytical-signal　amplifier.　The　fabricated　biosensor　was　examined　with　an　anodic　ECL　mode　using　tri-n-propyl　amine　as　the　coreactant.　The　construction　of　the　biosensor　was　systematically　characterized　with　various　techniques　including　atomic-force　microscopy,　gel　electrophoresis,　cyclic　voltammetry,　and　electrochemical-impedance　spectroscopy,　and　its　performance　was　optimized　under　a　variety　of　experimental　conditions,　especially　the　concentration　of　each　reagent　as　well　as　the　incubation　time.　Under　the　optimal　experimental　conditions,　the　reported　biosensor　showed　a　very　low　limit　of　detection　of　0.10　fM　(S/N　=　3)　and　a　wide　linear　dynamic　range　covering　0.50　fM　to　100　pM　toward　microRNA-155　with　excellent　specificity,　stability,　and　reproducibility.　Finally,　the　biosensor　was　successfully　applied　to　the　detection　of　microRNA-155　extracted　from　the　colon-cancer　cell　line　DLD1,　demonstrating　its　potential　application　in　the　sensitive　detection　of　biological　samples　in　the　early　diagnosis　of　diseases.