The　microRNA　profiles　within　living　cells　are　informative　for　diagnosis　and　prognosis　of　human　cancers.　In　the　present　work,　we　developed　a　new　sensing　strategy　based　on　branched　DNA　junction-enhanced　isothermal　circular　strand　displacement　polymerization　(B-ICSDP)　for　the　detection　and　intracellular　imaging　of　microRNAs　in　living　cells　of　interest.　A　circular　DNA　template　consisting　of　three　repetitive　fragments　serves　as　the　scaffold　for　the　self-assembly　of　sophisticated　signaling　probes,　resulting　a　shrunk　branched　DNA　junction.　Target　microRNA　triggers　the　opening　of　molecular　beacon,　not　only　restoring　the　quenched　fluorescence　but　also　activating　a　circular　polymerization-based　strand　displacement　reaction.　Thus,　patulous　branched　DNA　junction　is　abundantly　formed,　generating　the　amplified　signal.　It　is　noteworthy　that　great　heaps　of　branched　product　assemblies　can　be　also　achieved　in　living　cells,　and　the　intracellular　enzymatic　assembly　based　strategy　is　able　to　be　used　to　recognize　specific　microRNA-expressed　cancer　cells.　Moreover,　different　microRNAs　coexisting　in　the　same　living　cells　can　be　simultaneously　screened　without　any　interference　from　each　other　by　confocal　laser　scanning　microscopy.　The　measured　data　from　confocal　fluorescence　imaging　of　different　cancer　cells　demonstrates　that　the　B-ICSDP-based　system　is　a　promising　alternative　for　in　vivo　analysis　of　microRNAs　in　complicated　biological　samples.　Copyright　©　2018　American　Chemical　Society.