Prostate-specific　antigen　(PSA),　a　glycoprotein　that　is　most　likely　to　cause　prostate　cancer,　has　attracted　widespread　attention　in　recent　years　due　to　its　increasing　threat　to　people＇s　lives　and　health.　Herein,　we　developed　a　new　signal-amplified　photoelectrochemical　(PEC)　immunosensing　method　for　quantitative　monitoring　of　the　target　PSA　based　on　the　ion-exchange　reaction　for　the　in　situ　formation　of　ZnO/CdS/Ag2S　nanohybrids　triggered　by　the　as-released　silver　ions　(Ag+)　from　silver　nanolabels.　Initially,　the　introduction　of　a　target　PSA　caused　the　formation　of　a　sandwich　immunocomplex　in　an　anti-PSA　capture　antibody　(cAb)-coated　microplate　with　the　help　of　a　silver　nanoparticle-labeled　detection　antibody　(AgNPs-dAb).　Thereafter,　the　introduced　AgNPs　were　dissolved　with　acid　to　release　numerous　silver　ions.　In　this　regard,　an　ion-exchange　reaction　occurred　between　the　silver　ions　and　ZnO/CdS　nanorods　on　the　photosensitive　electrode,　thus　producing　ZnO/CdS/Ag2S　nanohybrids　to　generate　a　relatively　strong　photocurrent.　Under　optimal　conditions,　the　ion-exchange　reaction-based　PEC　immunoassay　exhibited　a　good　linear　range　of　0.05-50　ng　mL(-1)　and　allowed　the　detection　of　the　target　PSA　at　a　concentration　as　low　as　0.018　ng　mL(-1).　In　addition,　the　PEC　immunoassay　displayed　satisfactory　repeatability,　high　specificity,　and　acceptable　method　accuracy.　Importantly,　the　ion-exchange　reaction-based　PEC　immunoassay　provides　a　new　perspective　for　the　detection　of　other　disease-related　biomarkers　by　controlling　the　corresponding　antibodies.