MicroRNAs　(miRNAs)　are　considered　as　the　potential　biomarkers　for　many　cancers.　To　determine　miRNAs　in　cancer　cells　is　significant　for　realizing　these　diseases.　In　this　work,　a　microfluidic　paper-based　laser-induced　fluorescence　sensor　based　on　duplex-specific　nuclease　(DSN)　amplification　was　developed　and　applied　to　selectively　and　sensitively　determine　miRNAs　in　cancer　cells.　An　interface　for　laser-induced　fluorescence　detection　was　firstly　applied　to　perform　the　sample　detection　on　the　paper-based　chip.　Under　the　optimal　conditions,　DSN　(3　mu　L　0.10　U)　and　Taqman　probes　(2　mu　L　2.5　x　10(-7)　M)　were　preserved　on　the　circles　(Diameter　4　mm)　of　the　folded　paper　chip.　When　miRNA　solution　was　added,　the　mixed　solution　could　trigger　fluorescence　signal　amplification　by　cyclically　digesting　hybrids　of　miRNAs　and　Taqman　probes　by　DSN.　The　whole　determination,　including　sample　heating　process,　could　be　accomplished　within　40　min.　The　detection　limits　for　miRNA-21　and　miRNA-31　were　0.20　and　0.50　fM　respectively,　corresponding　to　only　1.0　and　1.5　zmol　consumption　of　miRNAs.　The　testing　of　mismatched　miRNAs　showed　that　the　method　had　good　specificity.　Finally,　the　method　was　applied　to　determine　miRNA-21　and　miRNA-31　in　lysates　of　cancer　cells　of　A549　and　HeLa,　and　hepatocyte　LO2.　MiRNA-21　and　miRNA-31　could　be　successfully　found　from　the　two　cancer　cells.　The　concentrations　for　miRNA-21　and　miRNA-31　were　1.74　x　10(-13)　M　and　6.29　x　10(-14)　M　in　HeLa　cell　lysate　(3.75　x　10(4)　cells/mL),　3.07　x　10(-15)　M　and　3.28　x　10(-15)　M　in　A549　cell　lysate　(8.33　x　10(6)　cells/mL)　respectively.　The　recoveries　ranged　from　87.30%　to　111.83%,　indicating　the　results　were　reliable.　The　developed　method　was　effective,　selective　and　sensitive　in　the　determination　of　miRNAs　in　cancer　cells.