A photoelectrochemical aptamer sensor for the detection of oxytetracycline(OTC) was constructed with nano-TiO2/graphene composites as photoelectric sensor substrate.Firstly,the nano TiO2 was synthesized by hydrothermal method on the fluorine doped tin dioxde(FTO） conductive glass.Then the graphene oxide was reduced to graphene by the simple electrochemical method,which was deposited on the surface of TiO2/FTO.The morphology of the obtained TiO2/graphene composites was characterized by scanning electronic microscopy(SEM).The electrochemical working station was applied to measure the photoelectric response.Results showed that the TiO2/graphene composite material could obviously increase the photoelectric current and improve the sensitivity.Based on the fact that the oxytetracycline aptamer could specifically recognize oxytetracycline,it was immobilized on the surface of TiO2/graphene nanocomposite modified FTO electrode for oxytetracycline detection.The method was applied in the detection of oxytetracycline with a linear range of 5.0×10-9-5.0×10-6 mol/L(r=0.988 7) and a detection limit of 1.0×10-9 mol/L.With the advantages of simplicity,low cost and wide linear range,the method is applicable for the determination of oxytetracycline residues in real samples.