This　work　reported　a　split-type　photoelectrochemical　(PEC)　immunoassay　for　the　detection　of　carcinoembryonic　antigen　(CEA)　based　on　target-induced　biocatalytic　precipitation　(BCP)　by　using　In2O3/CdIn2S4　heterojunctions　as　the　photosensitizers.　The　synthesized　In2O3/CdIn2S4　heterojunctions　improved　the　efficiency　of　charge　separation　and　shortened　the　electron　convey　path　to　enhance　the　photocurrent,　thus　exhibiting　high　conductivity　and　low　complexation　rates　of　photogenerated　electrons　and　holes.　In　the　presence　of　CEA,　horseradish　peroxidase　(HRP)　catalyzed　4-chloro-1-naphthol　(4-CN)　to　produce　benzo-4-chloro-hexadienone　(4-CD)　through　H2O2.　Then,　4-CD　was　deposited　onto　the　surface　of　In2O3/CdIn2S4　to　reduce　the　photocurrent　and　realized　the　signal　amplification.　The　PEC　immunoassay　revealed　an　excellent　photocurrent　toward　target　CEA　within　a　wide　range　of　0.01–50　ng　mL−1　at　a　low　limit　of　detection　of　2.8　pg　mL−1　under　the　optimum　conditions.　Multiple　switching　light　excitation　tests　demonstrated　the　good　reliability　and　stability　of　the　fabricated　PEC　biosensor.　The　accuracy　was　acceptable　in　comparison　with　human　CEA　enzyme-linked　immunosorbent　assay　(ELISA)　kit.　©　2022　Elsevier　B.V.