MicroRNAs　(miRNAs)　play　important　roles　in　physiological　and　pathological　processes　of　cells.　To　develop　a　fast,　simple　and　sensitive　method　to　determine　miRNAs　is　significant　for　miRNA　studies.　In　this　work,　determination　of　microRNA-122　(miR-122)　was　achieved　by　laser-induced　fluorescence　(LIF)　detection.　A　vial-LIF　interface　was　first　applied　for　sample　analysis.　A　two-step　amplification　of　the　fluorescence　signal　for　miR-122　was　designed　and　realized　by　applying　duplex-specific　nuclease　in　the　cleaving　of　two　sensing　probes.　Under　optimized　conditions,　the　analysis　of　a　miR-122　sample　could　be　completed　in　less　than　50　min.　Only　10　mu　L　sample　was　required　for　each　test　and　the　detection　limit　for　the　method　was　0.60　pM　equal　to　1.2　amol　of　miR-122　in　10　mu　L　solution.　Lastly,　the　developed　method　was　successfully　applied　to　determine　miR-122　in　chicken　and　duck　liver.　The　developed　method　was　fast,　selective,　sensitive　and　sample-saving　for　the　determination　of　miRNAs.