A　novel　p-type　semiconductor　material　(p-CuBi2O4)　is　designed　for　the　construction　of　split-type　photoelectrochemical　(PEC)　immunosensor　for　alpha-fetoprotein　(AFP)　with　the　hemin　assistant　to　enhance　the　cathodic　photocurrent.　Initially,　the　photocathode　of　PEC　immunosensor　is　fabricated　by　p-CuBi2O4　on　a　layer　of　gold　nanoparticles　(AuNPs,　as　a　front　contact　of　p-CuBi2O4)　to　enhance　the　efficiency　of　charge　separation.　In　the　presence　of　target　AFP,　a　sandwich-type　immunoreaction　was　carried　out　in　capture　antibody-coated　microplate　by　using　detection　antibody　and　hemin-based　G-quadruplex　(labeled　on　the　AuNP)　as　the　signal　probe.　Upon　exonuclease　I　(Exo　I)　introduction,　the　enzyme　digested　the　hemin/G-quadruplex-based　DNAzyme　to　release　the　hemin[Fe(III)],　which　captured　the　generated　electrons　of　p-CuBi2O4-based　photocathode　to　enhance　photocurrent　via　the　reduction　of　hemin[Fe(III)]　to　hemin[Fe(II)]　in　PEC　detection　system.　Under　the　optimal　conditions,　the　split-type　photocathodic　immunosensor　showed　a　wide　linear　dynamic　range　from　50 pg mL−1　to　20 ng mL−1　at　a　limit　of　detection　(LOD)　of　14.7 pg mL−1　toward　target　AFP.　Moreover,　the　PEC　immunosensor　also　displayed　high　specificity　and　good　reproducibility.　Favorably,　method　accuracy　was　evaluated　to　analyze　human　serum　specimens,　and　gave　matched-well　results　in　comparison　with　commercially　available　enzyme-linked　immunosorbent　assay　(ELISA)　method.　©　2017　Elsevier　B.V.