D-A　F8BT/g-C3N4　type　II　heterojunction　nanocomposite　was　employed　as　photoelectrode　material　for　photoelectrochemical　(PEC)　aptasensor　based　on　rolling　circle　amplification　(RCA)　with　the　assistance　of　3D-printed　device　for　carcinoembryonic　antigen　(CEA)　detection.　D-A　type　F8BT　improved　photocurrent　response　of　g-C3N4　nanosheet　after　forming　D-A　F8BT/g-C3N4　type　II　heterojunction　which　effectively　constructed　built-in　electric　field　and　reduced　electron-hole　recombination.　With　the　introduction　of　DNA-AuNP　probes　by　π-stacking　interaction,　the　local　plasmon　resonance　(LSPR)　of　AuNPs　enhanced　local　electric　field,　promoted　the　generation　of　electron-hole　and　further　improved　photocurrent　response.　When　target　CEA　was　in　presence　of　sensing　platform,　sandwich　construction　was　formed　between　two　kinds　of　CEA　aptamers　and　CEA　on　magnetic　beads,　triggering　the　RCA　reaction　to　produce　repeated　sequences.　Partial　sequences　of　complementary-DNA　in　combination　with　RCA　results　was　digested　by　Exo　III　enzyme　to　release　signal-DNA,　detaching　DNA-AuNP　probes　from　the　surface　of　the　F8BT/g-C3N4　by　complementation,　causing　the　attenuation　of　LSPR　and　the　decrease　of　photocurrent　response.　Combing　with　3D-printed　device,　this　PEC　aptasensor　exhibited　a　linear　response　to　CEA　from　0.02　ng　mL−1　to　50　ng　mL−1　with　detection　limit　of　6.7　pg　mL−1,　contributing　to　develop　all　organic　polymer　semiconductors　as　photoelectric　materials　in　PEC　study.　©　2020　Elsevier　B.V.