A　novel　approach　for　ultrasensitive　ochratoxin　A　(OTA)　detection　is　reported　based　on　dark　field　microscope-based　single　nanoparticle　identification　coupled　with　a　statistical　analysis　method.　OTA　aptamers　were　firstly　hybridized　with　a　singlestranded　DNA　(DNA1)　to　form　an　identification　probe　(DNA1-Apt).　The　aptamers　separate　from　DNA1　in　the　presence　of　OTA　and　are　released　from　the　identification　probe.　Then,　another　single-stranded　DNA　(DNA2)　hybridizes　with　DNA1　and　result　in　the　aggregation　of　gold　nanoparticles　(AuNPs).　Therefore,　the　presence　of　AuNP　aggregates　is　the　evidence　of　the　presence　of　OTA,　while　AuNP　aggregates　can　be　easily　identified　together　with　the　monomers　under　dark　field　microscopic　inspection.　On　the　other　hand,　by　counting　the　aggregation　rate　(the　number　of　AuNP　aggregates　versus　the　number　of　AuNP　monomers)　with　a　statistical　analysis　method,　OTA　could　be　quantitatively　detected.　The　detection　range　for　OTA　was　0.1　pg/　mL　similar　to　30　ng/mL　and　the　limit　of　detection　was　0.1　pg/mL.　The　proposed　sensor　has　comparative　detection　performance　to　sensors　utilizing　a　number　of　signal　amplification　procedures,　with　the　additional　advantages　of　simplicity　and　high　efficiency.　The　sensor　can　also　be　adopted　for　other　target　detection　simply　by　replacing　the　identification　probes.