STAT3　plays　an　important　role　in　regulating　gene　expression　and　is　closely　related　with　cancer.　Thus,　the　sensitive　and　specific　detection　of　the　STAT3　biomarker　is　of　great　importance　for　disease　diagnosis　and　therapeutics.　In　this　study,　by　combining　the　target　recycling　amplification　(TRA)　with　strand　displacement　amplification　(SDA),　we　have　developed　a　label-free　and　highly　sensitive　method　for　the　dual-amplified　detection　of　STAT3.　The　assay　system　consists　of　polymerization　primer　and　label-free　hairpin　probe　(HP)　containing　palindromic　fragment　and　nicking　site.　In　the　presence　of　STAT3,　the　stem　of　the　HP　is　opened,　followed　by　the　primer　binding　to　initiate　TRA　and　SDA　with　the　help　of　Klenow　Fragment　(KF)　and　nickase.　After　multiple　replication,　nicking,　and　strand　displacement,　STAT3　was　released　and　initiated　the　next　round　of　reactions,　generating　a　large　number　of　terminal　palindrome-contained　fragments.　Subsequently,　the　intermolecular　hybridization　between　palindromic　fragments　occurred　and　the　bidirectional　extension　by　polymerase　takes　place,　forming　the　dsDNAs.　The　double-stranded　DNA　products　can　be　quantified　by　measuring　the　fluorescence　intensity　of　SYBR　Green　I.　The　proposed　strategy　shows　the　excellent　specificity　and　high　sensitivity　with　a　detection　limit　as　low　as　50　pM.　In　addition,　this　designed　protocol　can　be　successfully　applied　to　detect　the　STAT3　in　human　serum,　indicating　great　potential　for　the　practical　application　in　early　diagnosis　and　prognosis.