CRISPR/Cas12a,　as　a　powerful　and　programmable　biosensing　tool,　has　brought　great　convenience　in　visual　detection　of　the　target　in　a　sequence-specific　mode.　Though　fluorescent　output　is　the　predominant　way　of　present　visual　methods,　this　strategy　highly　depends　on　cleaving　fluorophore-/quencher-labeled　oligonucleotides.　Few　research　focuses　on　realizing　fluorescent　visual　detection　without　DNA-labeling.　Herein,　we　have　proposed　a　CRISPR/Cas12a-based　label-free　fluorescent　visual　detection　strategy.　The　basic　principle　of　this　strategy　is　that　G-quadruplex　can　enhance　the　fluorescent　emission　of　fluorescent　ligands　while　dsDNA　target-activated　Cas12a　make　them　impotent　by　disrupting　the　higher-ordered　structure.　After　comparing　four　kinds　of　G-quadruplex-specific　ligands,　we　selected　Thioflavin　T　(ThT)　to　achieve　the　visual　observation　goal.　The　application　feasibility　was　confirmed　by　combining　with　loop-mediated　isothermal　amplification　(LAMP)　for　detection　of　Vibrio　parahaemolyticus　(V.　parahaemolyticus),　and　it　demonstrated　a　high　sensitivity　(1.36　×　102　copies)　and　specificity　(among　12　kinds　of　bacteria).　The　method　displayed　similar　performance　as　the　real-time　PCR　for　detection　of　real　samples　yet　had　lower　requirement　on　the　instrument.　The　signal　output　format　could　also　distinguish　Salmo　salar　from　other　seven　kinds　of　sequence-similar　Salmonidae.　The　findings　and　strategy　proposed　in　this　manuscript　will　expand　the　application　of　CRISPR/Cas12a-based　label-free　fluorescent　analysis.　©　2022　Elsevier　B.V.