Based on backbone-modified molecular beacons and duplex-specific nuclease, we have developed a target recycling amplification method for highly sensitive and selective miRNA detection. The combination of a low fluorescence background of 2-OMe-RNA modified MB and nuclease-assisted signal amplification leads to ultrahigh assay sensitivity, and the powerful discriminating ability of MB enables the differentiation of highly similar miRNAs with one-base difference, both of which are of great significance to miRNA detection.