The　complex　synthesis　of　photoelectric　materials　and　the　difficulty　of　fixing　the　identification　elements　on　the　photoelectrode　are　long-standing　problems　in　the　field　of　photoelectrochemical　(PEC)　biosensing.　In　this　work,　a　simple　PEC　aptasensor　construction　strategy　based　on　a　sulfur-doped　g-C3N4　(SCN)/n-GaN　heterostructure　photoelectrode　was　proposed.　The　SCN/n-GaN　heterostructure　can　be　formed　through　self-assembly　in　solution　since　SCN　can　be　uniformly　dispersed　in　solution.　In　addition,　as　a　dual-function　mediate,　an　aptamer　can　be　fixed　on　an　SCN　substrate　automatically　because　of　the　good　adsorption　performance　of　SCN.　Therefore,　tedious　steps　of　PEC　electrode　preparation　and　the　fixing　of　recognition　elements　were　both　avoided.　Compared　with　the　traditional　ones,　the　construction　difficulty　and　time　cost　of　the　prepared　PEC　aptasensors　are　greatly　reduced.　The　simplified　experimental　process　improves　the　stability　and　reproducibility　of　the　aptasensor.　Finally,　tetracycline　(TET)　was　used　as　a　model　target　to　verify　the　sensing　performance　of　the　proposed　PEC　strategy.　TET　can　consume　the　photogenerated　holes　of　the　SCN/n-GaN　heterostructure,　promote　carrier　migration,　and　result　in　the　change　in　the　photocurrent.　The　linear　relationship　between　the　change　in　the　photocurrent　intensity　and　the　TET　concentration　can　be　used　to　detect　TET.　The　aptasensor　has　a　linear　range　of　0.10-10.0　nmol　L-1　and　the　detection　limit　is　0.030　nmol　L-1　(3S/N).　The　aptasensor　was　applied　to　the　detection　of　TET　in　milk　samples　with　satisfactory　results.　©　2022　American　Chemical　Society