The　availability　of　sensing　platforms　able　to　rapidly　measure　abused　drugs　directly　in　biological　fluids　in　a　single　step　would　allow　performing　drugged　driving　screening　on　the　site.　The　achievement　of　this　goal　is　extremely　important　for　preventing　and　controlling　drug　abuse　and　crime　incidence.　Motived　by　this,　we　constructed　a　simple,　cost-effective　and　reagentless　electrochemical　aptamer-based　(EAB)　sensor　with　methamphetamine　(MAMP)　as　the　target　molecule.　This　EAB　sensor　produced　a　nanomolar　level　of　detection　accuracy　in　unprocessed　or　minimally　processed　bio-samples.　Specifically,　circular　dichroic　spectrum　was　used　to　confirm　that　the　truncated　aptamer　from　the　original　sequence　would　undergo　large　binding-induced　conformational　changes.　We　then　engineered　the　aptamer　to　work　in　the　EAB　platform　and　the　resulting　sensor　enabled　sensitive　and　specific　detection　of　MAMP　with　the　detection　limit　of　30　nM　in　undiluted　serum,　50　nM　in　undiluted　urine　and　20　nM　in　50%　saliva.　The　sensor　has　good　recovery　rate,　implying　this　method　has　good　reliability　and　repeatability.　The　detection　limit　is　far　below　the　clinical　detection　threshold,　it　would　be　hopefully　used　for　preliminary　screening　of　drugged　driving　in　real　world.