We　herein　developed　a　novel　biosensor　for　the　visual　detection　of　trace　uranyl　ion　(LION　in　aqueous　environment　with　high　sensitivity　and　specificity　by　using　DNAzyme-functionalized　magnetic　beads　(MBs)　for　UO22+　recognition　and　gold　nano-particles　(AuNPs)-based　enzymatic　catalysis　oxidation　of　TMB　(3,3＇,5,5＇-tetramethylbenzidine　sulfate)　for　signal　generation.　The　utilization　of　MBs　facilitates　the　magnetic　separation　and　collection　of　sensing　system　from　complex　sample　solution,　which　leads　to　more　convenient　experimental　operation　and　more　strong　resistibility　of　the　biosensor　to　the　matrix　of　sample,　and　the　utilization　of　AuNPs-based　enzymatic　catalysis　amplification　greatly　improved　the　sensitivity　of　the　biosensor.　Compared　with　the　previous　DNAzyme-based　UO22+　sensors,　the　proposed　biosensor　has　outstanding　advantages　such　as　relative　high　sensitivity　and　specificity,　operation　convenience,　low-cost　and　more　strong　resistibility　to　the　matrix　of　sample.　It　can　be　used　to　detect　as　low　as　0.02　ppb　(74　pM)　of　UO22+　in　aqueous　environment　by　only　naked-eye　observation　and　1.89　ppt　(7.0　pM)　of　UO22+　by　IN-visible　spectrophotometer　with　a　recovery　of　93-99%　and　a　RSD　＜=　5.0%　(n=6)　within　3　h.　Especially,　the　visual　detection　limit　of　0.02　ppb　(74　pM)　is　much　lower　than　the　maximum　allowable　level　of　UO22+　(130　nM)　in　the　drinking　water　defined　by　the　U.S.　Environmental　Protection　Agency　(EPA),　indicating　that　our　method　meets　the　requirement　of　rapid　and　on-site　detection　of　UO22+　in　the　aqueous　environment　by　only　naked-eye　observation.　(C)　2015　Elsevier　B.V.　All　rights　reserved.