TiO2-graphene nanocomposite was prepared by hydrolysis of titanium isopropoxide in colloidal suspension of graphene oxide and in situ hydrothermal treatment. It provides an efficient and facile approach to yield nanocomposite with TiO2 nanoparticles uniformly embedded on graphene substrate. The electrochemical behavior of adenine and guanine at the TiO2-graphene nanocomposite modified glassy carbon electrode was investigated. The results show that the incorporation of TiO2 nanoparticles with graphene significantly improved the electrocatalytic activity and voltammetric response towards these species comparing with that at the graphene film. The TiO2-graphene based electrochemical sensor exhibits wide linear range of 0.5–200μM with detection limit of 0.10 and 0.15μM for adenine and guanine detection, respectively. The excellent performance of this electrochemical sensor can be attributed to the high adsorptivity and conductivity of TiO2-graphene nanocomposite, which provides an efficient microenvironment for electrochemical reaction of these purine bases.