Lab-based　testing　systems　utilizing　photoelectrochemical　(PEC)　biosensing　methodologies　for　the　ultrasensitive　carcinoembryonic　antigen　(CEA)　have　been　developed,　although　the　majority　have　shown　complicated　operating　procedures　and　dependence　on　precise　apparatus.　Herein,　a　portable　photoelectrochemical　split　diagnostic　platform　based　on　a　hollow　CdS/CdMoO4　(h-CdS@CdMoO4)　shell-shell　structured　photoanode　system　was　developed　for　ultrasensitive　detection　of　CEA.　Using　a　small　LED　flashlight　as　the　excitation　light　source　and　a　digital　multimeter　(DMM)　as　the　signal　readout　device,　real-time　CEA　on　a　paper-based　printed　screen　electrode　developed　in-house　was　quickly　detected.　The　composite　h-CdS@CdMoO4　featured　a　special　hollow　shell-shell　heterojunction　structure　that　optimizes　photon　usage　in　the　bulk　phase　on　the　one　hand,　and　facilitates　directed　separation　of　the　electrons　and　holes　therein　on　the　other.　A　split-sandwich　immunoassay　and　detection　antibodies　for　modified　glucose　oxidase　were　introduced　into　the　paper-based　photoanode　test　system,　and　the　signals　were　displayed　with　a　DMM　to　realize　a　point-of-care　test　for　CEA.　Under　optimized　conditions,　the　constructed　portable　PEC　sensing　system　was　sensitive　to　the　target　CEA　from　0.02　to　50.0　ng　mL−1　with　a　detection　limit　of　11.3　pg　mL−1.　Interferent　experiments　and　stability　test　evaluations　demonstrate　the　specificity　and　robustness　of　the　constructed　paper-based　portable　PEC　sensor.　The　portable,　paper-based　PEC　immunoassay　system　developed　offers　a　fresh　way　of　exploring　affordable,　approachable　sensors　to　satisfy　both　the　relevant　community　medical　testing　demands　and　hospital　objectives　for　quick　testing.　©　2022　Elsevier　B.V.