Effective　and　sensitive　microRNA　detection　is　a　great　challenge.　Most　microRNA　assays　use　an　amplification　strategy　to　obtain　high　sensitivity,　which　makes　them　complicated.　Herein,　we　present　a　simple　and　amplification-free　solid-state　electrochemiluminescence　(ECL)　biosensor　for　the　detection　of　miRNA　based　on　high　effective　quenching　by　ferrocene　and　using　N-butyldiethanolamine　(BDEA)　as　a　more　effective　co-reactant.　Initially,　the　mixture　of　Nafion　and　Au　nanoparticles　(AuNPs)　was　cast　onto　the　glassy　carbon　electrode　(GCE)　to　form　a　Nafion-AuNPs　film.　The　resulting　electrode　was　then　immersed　into　a　solution　of　Ru(bpy)(3)(2+),　where　the　solid-state　Nafion-AuNPs/Ru(bpy)(3)(2+)　could　be　obtained　via　electrostatic　adsorption.　The　DNA　molecular　beacon,　which　was　modified　with　thiol　at　one　distal　and　the　other　was　labeled　with　ferrocene　(i.　e.,　Fc-MB),　was　covalently　attached　to　AuNPs　on　the　ECL　film　through　a　Au-S　bond.　Afterwards,　the　remaining　active　sites　of　nonspecific　adsorption　were　blocked　with　6-mercapto-1-hexanol　(MCH).　When　the　target　miRNA　was　present,　it　hybridized　with　the　complementary　part　in　the　loop　of　Fc-MB　and　formed　a　double-stranded　structure.　This　conformational　change　led　the　quencher　away　from　the　electrode,　resulting　in　a　remarkable　increase　in　ECL　intensity.　Under　the　optimum　condition,　the　ECL　signal　had　a　linear　relationship　with　miRNA　concentration　ranging　from　0.01　pM　to　1　x　10(3)　pM,　with　a　limit　of　detection　of　10　fM.　Moreover,　our　biosensor　showed　remarkable　specificity,　outstanding　reproducibility,　good　stability　and　excellent　performance　in　real　sample　investigation　with　no　amplification.　Therefore,　this　developed　strategy　has　great　potential　in　early　miRNA-related　cancer　diagnosis.