Aflatoxin　B-1　(AFB(1))　can　cause　great　threat　to　human　health,　so　the　development　of　convenient　and　portable　device　for　sensitive　detection　of　AFB(1)　is　highly　desired.　The　portable　pH　meter　has　the　characters　of　facile　operation,　low　cost,　and　easy　availability.　Therefore,　in　this　study,　we　investigate　the　applicability　of　utilizing　a　pH　meter　as　the　readout　to　develop　a　portable　sensor　for　AFB(1).　The　specific　detection　of　AFB(1)　is　realized　via　the　combination　of　AFB(1)-responsive　aptamer-cross-linked　hydrogel.　Upon　the　addition　of　AFB(1),　AFB(1)　binds　to　its　aptamer　with　high　affinity　in　lieu　of　aptamer/DNA　complex,　causing　the　collapse　of　hydrogel　network　and　results　in　the　releasing　of　urease　into　the　solution.　The　released　urease　can　catalyse　the　hydrolysis　of　urea　and　result　in　the　rise　of　pH　value.　The　change　of　pH　value　has　a　direct　relationship　to　the　concentration　of　AFB(1)　in　the　range　of　0.2-20　mu　M　with　a　detection　limit　of　0.1　mu　M　(S/N　=　3).　The　proposed　portable　device　is　successfully　applied　to　assay　AFB(1)　in　the　food　samples　with　satisfied　results.