MicroRNAs　(miRNAs)　are　involved　in　a　variety　of　biological　processes,　and　the　accurate　detection　of　miRNAs　is　of　great　importance　for　early　diagnosis　of　various　cancers.　Herein,　we　have　developed　a　highly　sensitive　method　for　the　intracellular　imaging　of　miRNAs　based　on　a　palindromic　probe-induced　strand　displacement　amplification　(pSDA).　The　sensing　element　is　a　partly　complementary　hybrid　consisting　of　two　DNA　components:　one　fluorescent　dye-labeled　signaling　probe　containing　a　palindromic　sequence　and　loop-based　target　recognition　site　and　one　quencher　moiety-attached　locking　probe.　In　the　presence　of　target　miRNA,　the　target　species　can　hybridize　with　the　loop　site　and　release　the　terminal　palindromic　fragment,　initiating　the　pSDA　reaction.　Thus,　a　considerable　amount　of　fluorescent　moieties　are　spatially　separated　from　the　quenchers,　generating　a　dramatically　enhanced　fluorescence　signal.　As　a　result,　the　target　miRNAs　can　be　quantified　down　to　25　pM　with　the　linear　response　range　over　four　orders　of　magnitude.　The　detection　specificity　is　high　enough　to　eliminate　the　interference　from　nontarget　miRNAs　and　other　biospecies　co-existing　in　samples,　and　thus　the　diseased　cells　are　easily　distinguished　from　healthy　cells.　Strikingly,　the　pSDA-based　system　possesses　the　desirable　capability　to　discriminate　tumor　cells　from　healthy　cells,　indicating　a　promising　diagnostic　tool　for　the　detection　of　cancers　and　other　diseases　in　early　stage.