A　magnetic-assisted　photoelectrochemical　(PEC)　and　colorimetric　(CL)　dual-modal　biosensing　platform　with　high　precision　was　established　to　monitor　prostate-specific　antigen　(PSA)　based　on　Bi2MoO6　nanosheets　(BMO)　by　coupling　the　aptamer-guided　hybridization　chain　reaction　(HCR)　with　the　hydrolysate-induced　vulcanization　reaction　of　Bi2MoO6　nanosheets.　Upon　addition　of　PSA,　trigger　DNA　(tDNA)　was　released　by　the　interaction　between　the　target　analyte　and　the　aptamer　and　then　further　hybridized　with　anchor　DNA　(aDNA)　conjugated　on　magnetic　beads　(MBs).　The　as-released　tDNA　initiated　the　target-assisted　HCR　in　the　presence　of　two　alternating　hairpin　sequences　(Bio-H1　and　Bio-H2)　to　produce　nicked　long　double-stranded　DNA　on　the　surface　of　MBs,　where　numerous　alkaline　phosphatase　(ALP)　enzymes　could　assemble　with　MBs　through　the　biotin-avidin　reaction,　resulting　in　the　hydrolysis　of　sodium　thiophosphate　(TP)　to　H2S.　The　as-produced　H2S　reacted　with　BMO　to　form　vulcanized　BMO　(BMO-S),　thus　leading　to　obvious　enhanced　PEC　performance　under　visible　light　with　the　color　change　from　light　yellow　to　brown.　Having　optimized　the　test　conditions,　the　magnetic-assisted　biosensing　system　holds　a　good　quantitative　diagnosis　sensitivity　area　in　a　range　of　5.0　pg　mL(-1)-100　ng　mL(-1)　with　a　calculated　detection　limit　down　to　3.5　pg　mL(-1).　Meanwhile,　a　visual　colorimetric　assay　on　basis　of　the　change　in　the　color　of　the　materials　was　also　realized.　Given　the　exceptional　performance　of　the　constructed　biosensor,　it　may　possess　great　promise　as　an　advanced　bioanalytical　tool　for　practical　applications.