Interactions between graphene and anatase TiO2 (110) surface with and without oxygen vacancy (V-O) are investigated by first-principle calculations. The close but non-destroyed contact at interface facilitates photo-excited electron transfer between graphene and TiO2. With a work function (WF) smaller than perfect TiO2 substrate, graphene is typically electron depleted. However, the introduction of surface VO decreases the WF of TiO2 remarkably and smaller than graphene, which induces electron transfer with reversed direction and accumulate at graphene sheet. Especially, the evident red shift of the optical absorption edge and obviously enhanced absorption intensity in the visible region for both combined configurations illustrate the enhancement mechanism of photocatalytic performance. (C) 2017 Elsevier B.V. All rights reserved.