Based　on　silver-enhanced　gold　nanoparticles　(AuNPs)　label　technique　that　AuNPs　could　specifically　catalyze　the　deposition　of　silver　ions　using　hydroquin　as　a　weak　reducing　agent,　an　efficient　and　sensitive　electrochemical　aptasensor　was　developed　for　detection　of　trace　okadaic　acid　(OA).　When　the　sample　solution　containing　OA,　the　OA　aptamer　dissociated　from　the　dsDNA　on　electrode　surface　due　to　the　specific　binding　between　OA　and　OA　aptamer,　AuNPs　labeled　signal　probe　(Sp)　could　hybridize　with　the　resulted　free　capture　probe　(Cp)　on　the　electrode　surface.　And　then,　the　electrode　was　immersed　in　a　silver　staining　reagent　to　perform　following　sliver　staining.　Finally,　the　oxidation　signal　of　the　nano-silver　was　directly　detected　by　square　wave　voltammetry　(SWV).　Under　the　optimal　experimental　conditions,　the　linear　range　of　the　established　OA　aptasensor　was　10.　0　pg/　mL　-500.　0　ng/　mL,　and　the　detection　limit　(3　sigma/k)　was　8.　8　pg/　mL.　The　sensor　was　applied　to　detection　of　mussels.　The　experimental　results　showed　that　the　content　of　OA　in　the　edible　part　of　mussels　was　36.　0　ng/　g,　which　was　lower　than　the　permitted　maximal　limit　of　European　Union　(160.　0　ng/　g),　and　the　recoveries　were　94.　2%-112.　0%　.