The　electrostatic　attraction　difference　between　negatively　charged　report　probes　and　positively　charged　electrode　had　been　applied　to　develop　a　signal-on　low　background　electrochemiluminescence　(ECL)　biosensor　for　microRNA-141　(miRNA141,　chosen　as　a　model　target)　detection.　Indium　tin　oxide　(ITO)　electrode　was　modified　with　poly-(allylamine　hydrochloride)　(PAH)　to　generate　a　positively　charged　surface.　The　electrostatic　repulsion　between　dichlorotris　(1,10-phenanthroline)　ruthenium　(II)　hydrate　(Ru(phen)(3)(2+))　and　ITO　electrode　results　in　the　low　background　signal.　The　target　can　trigger　an　enzyme-free　isothermal　catalytic　hairpin　self-assembly　(CHA)　and　hybrid　chain　reaction　(HCR)　cascade　reaction　to　generate　a　large　amount　of　negatively　charged　long　dsDNAs,　which　can　be　used　to　load　Ru(phen)(3)(2+)　(Ru-dsDNA)　with　high　efficiency.　Ru-dsDNA　complexes　are　negatively　charged　and　can　easily　accumulate　on　ITO　electrode　surface　because　of　electrostatic　attraction,　which　results　in　a　strong　ECL　signal　detected.　The　ECL　intensity　of　the　system　was　linearly　correlated　with　the　logarithm　of　microRNA-141　concentration　in　the　range　of　1　fM　similar　to　5　pM　with　a　detection　limit　of　0.17　fM　(S/N　=　3).　The　reliability　of　the　proposed　biosensor　had　been　verified　through　the　detection　of　targets　in　cell　lysates.