As　microRNAs　(miRNAs)　are　aberrantly　expressed　in　a　variety　of　cancers,　detecting　them　precisely　is　of　great　importance.　Here　we　constructed　a　sensitive　and　selective　enzyme-free　sensing　platform　for　miRNA　detection　based　on　target-catalyzed　hairpin　assembly　and　magnesium　ion-dependent　deoxyribozyme　(Mg2+-dependent　DNAzyme).　This　sensing　method　introduces　two　amplification　circuits　simultaneously　and　shows　a　low　detection　limit　of　1　pmol/L.　This　enzyme-free　method　is　especially　preferred　because　of　its　facility　and　economy.　Furthermore,　this　amplified　sensor　shows　high　selectivity　for　discriminating　perfectly　complementary　target　and　other　mismatched　RNAs.　Therefore,　the　established　strategy　could　be　used　as　a　simple,　sensitive　and　selective　method　for　target　miRNA　detection.　©　2015　Science　China　Press　and　Springer-Verlag　Berlin　Heidelberg.