In this paper, reconstructions and native defects of TiO2 anatase (101) surface are studied using the state-of-the-art theoretical method. We find that O interstitials are dominated defects at an oxidization environment. These O interstitials induce acceptor energy levels, corresponding to an indirect-direct band transition and a bandgap narrowing. And thus, the experimental result that an O-rich anatase TiO2 has the higher photocatalytic activity can be understood. The formation of O vacancies and Ti interstitials becomes feasible at a reduced condition, and reconstructed TiO2 anatase (101)-(1 x 1)structures present with increasing reduction degree. Furthermore, the Fermi levels of defected and reconstructed TiO2 anatse (101) can be modulated in a wide range (i.e., nearly the whole band gap), which are different from those of TiO2 rutile (110). (C) 2017 Elsevier B.V. All rights reserved.