The　complex　synthesis　of　photoelectric　materialsand　the　difficulty　offixing　the　identification　elements　on　thephotoelectrode　are　long-standing　problems　in　thefield　ofphotoelectrochemical　(PEC)　biosensing.　In　this　work,　a　simplePEC　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　insolution.　In　addition,　as　a　dual-function　mediate,　an　aptamer　can　befixed　on　an　SCN　substrate　automatically　because　of　the　goodadsorption　performance　of　SCN.　Therefore,　tedious　steps　of　PECelectrode　preparation　and　thefixing　of　recognition　elements　wereboth　avoided.　Compared　with　the　traditional　ones,　the　constructiondifficulty　and　time　cost　of　the　prepared　PEC　aptasensors　are　greatly　reduced.　The　simplified　experimental　process　improves　thestability　and　reproducibility　of　the　aptasensor.　Finally,　tetracycline　(TET)　was　used　as　a　model　target　to　verify　the　sensingperformance　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　thephotocurrent　intensity　and　the　TET　concentration　can　be　used　to　detect　TET.　The　aptasensor　has　a　linear　range　of　0.10-10.0　nmolL-1and　the　detection　limit　is　0.030　nmol　L-1(3S/N).　The　aptasensor　was　applied　to　the　detection　of　TET　in　milk　samples　withsatisfactory　results