The　＂turn-on＂　mode　surface-enhanced　Raman　scattering　(SERS)　aptasensor　for　ultrasensitive　ochratoxin　A　(OTA)　detection　was　developed　based　on　the　SERS　＂hot　spots＂　of　AuNanostar@4-MBA@Au　core-shell　nanostructures　(AuNS@4-MBA@Au)　and　exonuclease　III　(Exo　III)-assisted　target　cycle　amplification　strategy.　Compared　with　conventional　gold　nanoparticles,　AuNS@4-MBA@Au　provides　a　much　higher　SERS　enhancement　factor　because　AuNS　exhibits　a　larger　surface　roughness　and　the　lightning　rod　effect,　as　well　as　an　excellent　electromagnetic　field　between　the　AuNS　core　and　the　Au　shell,　which　contribute　to　the　superstrong　SERS　signal.　Meanwhile,　Exo　III-assisted　target　cycle　amplification　can　be　used　as　an　effective　method　for　the　further　amplified　detection　of　OTA.　Additionally,　the　utilization　of　streptavidin　magnesphere　paramagnetic　particles　offers　a　green,　economical,　and　facile　technology　for　the　accumulation　and　separation　of　the　signal　probe　AuNS@4-MBA@Au　from　solution.　All　these　factors　lead　to　a　significant　enhancement　of　detectable　signals　and　superhigh　sensitivity.　As　a　result,　the　limit　of　detection　as　low　as　0.25　fg　mL(-1)　could　be　achieved,　which　was　lower　than　that　in　the　other　reported　literatures　on　SERS　methods　for　OTA　detection　as　we　know.　The　developed　SERS　aptasensor　also　provides　a　promising　tool　for　foodstuff　detection.