Based　on　the　disruption　and　recovery　of　fluorescence　of　styryl　quinolinium　(SQ)　dye/G-quadruplex　complex,　a　label-free　method　for　dual-channel　detection　of　Ag+　and　cysteine　is　developed.　The　above　sensing　system　exhibits　high　sensitivity　and　good　selectivity　for　Ag+,　even　in　the　presence　of　other　metal　ions　(such　as　Na+,　Mg2+,　Mn2+,　Ba2+,　Ca2+,　Pb2+,　Zn2+,　Cd　2+,　Hg2+　and　Cu2+).　Due　to　cysteine　(Cys)　is　a　strong　Ag+-binder　and　competes　with　quadruplex-forming　G-rich　oligonucleotides　for　Ag+　binding,　and　results　in　the　reformation　of　G-quadruplex　structure　and　the　recovery　of　fluorescence.　Thus　SQ　dye/G-quadruplex　complexes　are　not　only　a　potential　primary　sensor　toward　Ag+,　but　also　a　secondary　sensor　toward　Cys.　Neither　the　Ag　+-sensing　nor　the　Cys-sensing　systems　required　labeled　oligonucleotides.　Under　the　optimal　conditions,　this　method　is　capable　of　detection　of　Ag+　in　the　range　of　0.1-15.0　μM　with　a　detection　limit　of　26.0　nM.　In　addition,　the　proposed　method　allows　a　good　response　to　cysteine　with　a　linear　range　of　0.008-10　μM,　and　the　limit　of　detection　is　found　to　be　2.0　nM.　Moreover,　this　method　has　been　applied　successfully　to　the　sensing　of　cysteine　in　human　urine　with　satisfactory　recovery.　©　2012　Elsevier　B.V.