A　competitive-displacement　reaction　strategy　based　on　target-induced　dissociation　of　gold　nanoparticle　coated　graphene　nanosheet　(AuNPs/GN)　from　CdS　quantum　dot　functionalized　mesoporous　titanium　dioxide　(CdS　QDs/TiO2)　was　designed　for　the　sensitive　photoelectrochemical　(PEC)　aptasensing　of　prostate-specific　antigen　(PSA)　through　the　exciton-plasmon　interaction　(EPI)　between　CdS　QDs　and　AuNPs.　To　construct　such　an　aptasensing　system,　capture　DNA　was　initially　conjugated　covalently　onto　CdS　QDs/TiO2-modified　electrode,　and　then　AuNPs/GN-labeled　PSA　aptamer　was　bound　onto　biofunctionalized　CdS　QDs/TiO2　via　hybridization　chain　reaction　of　partial　bases　with　capture　DNA.　Introduction　of　AuNPs/GN　efficiently　quenched　the　photocurrent　of　CdS　QDs/TiO2　thanks　to　energy　transfer.　Upon　addition　of　target　PSA,　the　sandwiched　aptamer　between　CdS　QDs/TiO2　and　AuNPs/GN　reacted　with　the　analyte　analyte,　thus　resulting　in　the　dissociation　of　AuNPs/GN　from　the　CdS　QDs/TiO2　to　increase　the　photocurrent.　Under　optimum　conditions,　the　aptasensing　platform　exhibited　a　high　sensitivity　for　PSA　detection　within　a　dynamic　linear　range　of　1.0　pg/mL　to　8.0　ng/mL　at　a　low　limitat　of　detection　of　0.52　pg/mL.　The　interparticle　distance　of　exciton-plasmon　interaction　and　contents　of　AuNPs　corresponding　to　EPI　effect　in　this　system　were　also　studied.　Good　selectivity　and　high　reproducibility　were　obtained　for　the　analysis　of　target　PSA.　Importantly,　the　accuracy　and　matrix　effect　of　PEC　aptasensor　was　evaluated　for　the　determination　of　human　serum　specimens　and　newborn　calf　serum-diluted　PSA　standards,　giving　a　well-matched　result　with　the　referenced　PSA　ELISA　kit.