Cd2+　is　one　of　the　most　toxic　heavy　metal　ions　that　can　be　easily　accumulated　in　human　body　via　food　chain.　Thus,　the　onsite　detection　of　Cd2+　in　food　is　very　important.　However,　present　methods　for　Cd2+　detection　either　require　the　use　of　large　equipment,　or　suffer　from　the　severe　interference　from　other　analogical　metal　ions.　This　work　establishes　a　facile　Cd2+　mediated　turn-on　ECL　method　for　highly　selective　detection　of　Cd2+　via　cation　exchanging　with　the　nontoxic　ZnS　nanoparticles,　owing　to　the　unique　surface-state　ECL　properties　of　CdS　nanomaterials.　The　linear　range　of　the　calibration　curve　is　from　7.0　x　10-8　to　1.0　x　10-6　M,　while　other　analogical　metal　ions　do　not　interfere,　facilitating　the　selective　detection　of　Cd2+　in　oyster　samples.　The　result　agrees　well　with　that　obtained　using　atomic　emission　spectroscopy,　indicating　the　potential　for　wider　application　of　this　approach.