A　new　photoelectrochemical　immunoassay　based　on　self-assembled　p-n　Ag2O@Bi2O2S　nanoflower　heterojunction　was　designed　and　developed　for　quantitative　monitoring　of　prostate-specific　antigen　(PSA)　in　biological　fluids.　Primarily,　self-assembled　p-n　Ag2O@Bi2O2S　nanoflower　heterojunctions　were　served　as　the　photoactive　materials　and　coated　onto　the　surface　of　electrodes.　Subsequently,　the　glucose　oxidase　(GOx)　was　bound　to　the　detection　antibody　(mAb2)　labeled　gold　nanoparticles　(Au　NPs)　and　then　were　employed　to　accomplish　a　sandwich-like　immunoreaction　to　generate　H2O2　on　a　microplate　incubated　with　monoclonal　anti-PSA　antibodies.　In　the　presence　of　PSA,　the　product　(H2O2)　was　catalyzed　by　the　substrate,　which　was　used　as　an　electron　sacrificial　agent　to　improve　signal　conversion　and　capture　of　photogenerated　electrons.　Under　optimum　conditions,　a　wide　linear　range　of　0.01-50　ng　mL-1　and　a　low　detection　limit　of　5.3　pg　mL-1　were　accomplished　with　the　sensor,　exhibiting　an　excellent　photocurrent　response.　Moreover,　the　proposed　sensor　revealed　satisfactory　reproducibility,　high　selectivity,　and　acceptable　accuracy　for　the　real　sample　testing.　Importantly,　our　work　provides　a　novel　strategy　for　high　sensitivity　detection　of　disease-associated　biomarkers　for　the　early　diagnosis　of　cancers.