Herein　a　versatile　photoelectrochemical　(PEC)　immunoassay　platform　for　sensitive　and　specific　screening　of　tumor　biomarkers　(carcinoembryonic　antigen;　CEA)　was　innovatively　designed　using　hollow　cadmium　sulfide　(H-CdS)　as　photoactive　matrix　based　on　immunomagnetic　separation.　Experimental　results　reveal　that　the　hollow-structure　prepared　by　template　hydrothermal-etching　method　endowed　the　CdS　with　better　photocurrent　intensity　compared　to　the　traditional　CdS　nanoparticles.　Upon　addition　of　target　CEA,　a　sandwiched　immunoreaction　was　carried　out　between　anti-CEA　capture　antibody-conjugated　immunomagnetic　bead　(IMB)　and　horseradish　peroxidase　(HRP)-labeled　anti-CEA　detection　antibody,　accompanying　the　immunocomplex　formation　of　the　IMB-antibody/CEA/HRP-labeled　antibody　(IMB-CEA-HRP).　Followed　by　magnetic　separation,　the　carried　HRP　on　the　sandwich　structure　triggers　enzymatic　bioetching　of　H-CdS,　thus　resulting　in　decreasing　photocurrent　intensity.　The　H-CdS-based　PEC　sensing　system　exhibited　satisfying　photocurrent　responses　toward　target　CEA　within　the　working　range　from　0.02　ng　mL(-1)　to　50　ng　mL(-1)　at　a　low　detection　limit　of　6.12　pg　mL(-1).　Combined　with　magnetic　immunoassay,　this　sensing　platform　has　the　advantages　of　high　precision,　great　anti-interference　ability,　and　acceptable　accuracy.　Overall,　this　research　not　only　provides　an　efficient　strategy　for　the　activity　of　CdS　with　a　well-defined　hollow-nanostructures　but　also　sheds　light　on　the　development　of　enzyme-triggered　bioetching　technology　for　traditional　PEC　immunoassay.