An　all-solid-state　metal-mediated　Z-scheme　photoelectrochemical　(PEC)　immunoassay　was　designed　for　sensitive　detection　of　prostate-specific　antigen　(PSA)　by　using　WO　3　-Au-CdS　nanocomposite　as　photoactive　material　and　copper　ion　(Cu　2+　)　as　an　inhibitor.　The　Z-scheme　PEC　system　comprising　of　CdS　nanoparticle　(photosystem　I;　PS　I),　WO　3　nanorod　(photosystem　II;　PS　II)　and　gold　nanoparticle　(Au　NP;　solid　electron　mediator)　was　reasonably　established　by　a　simple　and　green　synthetic　method.　As　an　important　part　of　Z-scheme　system,　the　sandwiched　gold　nanoparticles　between　electron　donor　materials　and　hole　provider　materials　could　accelerate　electron　transfer　from　positive　conduction　band　(CB)　of　WO　3　to　negative　valence　band　(VB)　of　CdS,　thus　resulting　in　high-efficient　separation　of　the　carriers.　In　the　presence　of　target　PSA,　a　sandwiched　immunoreaction　was　executed　between　capture　antibody-coated　microplate　and　CuO　nanoparticle-labeled　detection　antibody.　Thereafter,　CuO　nano　labels　were　dissolved　into　Cu　2+　ions　under　acidic　condition　to　decrease　the　photocurrent　of　Z-scheme　WO　3　-Au-CdS　thanks　to　the　formation　of　exciton　trapping　center　of　Cu　x　S　(x　=　1,2)　on　the　surface.　Under　optimum　conditions,　Z-scheme　PEC　immunoassay　exhibited　good　photocurrents　toward　target　PSA　within　a　linear　range　of　0.01–50　ng　mL　−1　at　a　limit　of　detection　of　1.8　pg　mL　−1　.　Moreover,　the　Z-scheme　PEC　immunoassay　had　high　selectivity　and　accuracy.　Importantly,　this　method　provides　a　new　horizon　for　detection　of　disease-related　biomarkers　with　high　sensitivity.　©　2019　Elsevier　B.V.