This　work　presented　an　innovative　and　rationally　engineered　palindromic　molecular　beacon　(PMB)　based　＂Z-scheme＂　photoelectrochemical　(PEC)　biosensing　protocol　for　the　selective　screening　of　kanamycin　(Kana)　through　DNA　hybridization-induced　conformational　conversion.　Interestingly,　the　ingeniously　designed　PMB　integrated　the　multifunctional　elements　including　recognition　region,　primer-like　palindromic　fragment,　and　polymerization-nicking　template.　The　cosensitized　structures　consisted　of　CdS　quantum　dot　functionalized　hairpin　DNA2　(QD-HP2)　and　region-selectively　deposited　gold　nanoparticles　onto　{001}　facets　of　bismuth　oxychloride　(Bi0C1-Au).　Compared　with　Bi0C1-Au　alone,　the　attachment　of　CdS　QDs　onto　Bi0C1-Au　(i.e.,　BiOC1-Au-CdS　QDs)　exhibited　evidently　enhanced　photocurrent　intensity　thanks　to　the　synergistic　effect　of　Z-scheme　BiOC1-Au-CdS　QDs.　After　incubation　with　target　Kana,　Kana-aptamer　binding　could　induce　the　exposure　of　PMB　region　for　hairpin　DNA1　(HP1).　The　exposed　palindromic　tails　hybridized　with　each　other　(like　a　molecular　machine)　to　consume　the　substrates　(dNTPs)　and　fuels　(enzyme)　for　the　releasing　of　numerous　nick　fragments　(Nick).　The　as　generated　nick　fragments　could　specifically　hybridize　with　the　complementary　region　of　QD-HP2,　thus　resulting　in　decreasing　photocurrent　because　of　the　increasing　spatial　distance　for　electron　transfer　between　two-type　photosensitizers.　Under　optimum　conditions,　the　PMB-based　sensing　system　exhibited　satisfying　photocurrent　responses　toward　target　Kana　within　the　working　range　from　50　to　5000　fM　at　a　low　detection　limit　of　29　fM.　Impressively,　the　concept　of　a　palindromic　fragment-mediated　primer-free　biosensing　strategy　offers　a　new　avenue　for　advanced　development　of　efficient　and　convenient　biodetection　systems.