A　fluorescent　aptasensor　for　the　Ochratoxin　A　(OTA)　assay,　which　combines　the　high　efficiency　of　hyperbranched　rolling　circle　amplification　(HRCA)　and　the　specific　recognition　of　the　aptamer　has　been　developed.　OTA　can　bind　with　the　aptamer　with　high　affinity,　which　hinders　hybridization　between　the　aptamer　and　capture　probe　DNA　(CDNA).　Then　the　free　CDNA　hybridizes　with　the　padlock　probe　and　initiates　a　HRCA　reaction.　The　HRCA　products　contain　large　amounts　of　double　strand　DNA　(dsDNA),　which　can　then　combine　with　SYBR　Green　I　to　produce　a　fluorescence　signal.　The　fluorescence　intensity　of　the　system　has　a　linear　relationship　with　the　logarithm　of　the　OTA　concentration　in　the　range　of　4　fg　mL-1　to　400　pg　mL-1　and　a　limit　of　detection　(LOD)　of　1.2　fg　mL-1　is　obtained.　The　fluorescent　aptasensor　was　applied　to　detect　OTA　in　corn　and　oat　samples　with　satisfying　results.　©　The　Royal　Society　of　Chemistry　2015.