MicroRNAs　(miRNAs)　are　desirable　targets　for　the　diagnosis,　prognosis　and　treatment　of　diverse　human　diseases.　In　this　study,　we　developed　a　universal　and　enzyme-free　signal　amplification　approach　for　the　quick,　sensitive　and　specific　electrochemical　detection　of　diverse　miRNAs　from　tumor　cells　using　a　catalyzed　hairpin　assembly　(CHA)　and　the　DNA　three-way　junction　(DNA　TWJ).　The　target　miRNA,　which　was　formed　as　an　initiator　through　specific　recognition,　periodically　triggered　the　assembly　of　two　hairpins　into　a　duplex　via　CHA.　Subsequently,　these　duplexes　induced　the　catalytic　assembly　of　the　DNA　three-way　junction　and　the　release　of　the　methylene　blue-labeled　DNA　strand　S　(S-MB).　Thereafter,　the　S-MB　was　captured　using　the　electrode　through　hybridization　with　the　capture　probe　to　generate　a　notable　current　response.　The　proposed　biosensor　could　be　switched　in　response　to　different　miRNA　targets　by　changing　the　specific　sequence　of　H0.　These　findings　indicate　its　ability　to　distinguish　single　base　mismatch　miRNAs　and　analyze　miRNAs　extracted　from　cells.　Therefore,　the　universal　and　enzyme-free　signal　amplified　electrochemical　method　described　herein　can　be　potentially　useful　in　diverse　miRNA-related　clinical　analysis　and　disease　diagnosis.　©　2020　The　Royal　Society　of　Chemistry.