The　flap　endonuclease　1　(FEN1)　plays　a　key　role　in　DNA　replication　and　repair,　its　aberrant　expression　is　associated　with　tumor　development,　so　it　has　been　recognized　as　a　promising　biomarker　for　a　variety　of　cancers.　Here,　a　novel　＂turn　on＂　mode　gold　nanocube-enhanced　surface-enhanced　Raman　scattering　(SERS)　biosensor　was　constructed　by　combining　a　heated　Au　electrode　(HAuE),　exonuclease　III　(Exo　III)-assisted　cycle　amplification,　and　gold　nanocube　(AuNC)-based　SERS　enhancement　to　achieve　highly　sensitive　detection　of　FEN1　activity.　The　SERS　tag　was　prepared　using　the　Raman　reporter　modified　on　the　AuNC　surface,　and　the　high　electromagnetic　field　provided　by　the　sharp　geometric　feature　of　AuNC　greatly　enhanced　the　SERS　signal.　At　the　same　time,　HAuE　was　used　to　increase　the　electrode　surface　temperature　and　enhance　the　FEN1　activity,　leading　to　more　trigger　DNA　being　cleaved,　which　was　used　to　initiate　the　Exo　III-assisted　cycle　amplification.　Taking　all　these　advantages,　the　proposed　method　possessed　high　sensitivity　and　good　selectivity,　with　a　low　limit　of　detection　(LOD)　of　3.19　x　10-　7　U　mu　L-　1.　In　addition,　this　method　was　successfully　applied　to　detect　FEN1　activity　in　real　cellular　extracts.