Effective　drugged　driving　screening　by　the　roadside　requires　simple-to-use　sensing　platforms　that　allow　accurate　measurement　of　drugs　from　biofluids.　Achieving　this　goal　is　of　vital　importance　to　prevent　and　control　the　incidence　of　drug　abuse,　traffic　accidents　and　crime.　Given　this,　we　designed　a　rapid,　sensitive　and　reagentless　electrochemical　aptamer-based　(EAB)　sensor　to　detect　ketamine.　This　platform　produced　nanomolar　detection　accuracy　and　reliable　results　were　obtained　within　30　s.　To　design　a　sensitive　platform,　circular　dichroism　(CD)　was　used　to　screen　the　aptamer　which　underwent　the　largest　binding-induced　conformational　change.　In　addi-tion,　kinetic　differential　measurement　(KDM)　was　utilized　to　improve　the　signal　gain　of　the　EAB　sensor.　The　constructed　sensing　platform　achieved　sensitive　and　specific　detection　of　ketamine　in　50　%　saliva　and　undiluted　urine　with　detection　limits　as　low　as　10　nM,　which　was　much　lower　than　the　physiological　detection　threshold.　Hence　the　present　EAB　sensor　is　expected　to　be　applied　in　the　preliminary　drugged　driving　screening　in　the　real　world.