To improve the photocatalytic activity of narrow-gap material Bi2O3, efforts need be made to lower the electron-hole recombination rate and widen the response range of visible light. Understanding the related mechanism is vital, which may lead to high electron-hole mobility and suitable band edge. In this paper we have studied the atomic and electronic structure of single metallic atom (Ag, Cu, Pb, Pd, Sn)-doped and nitrogen (N)-metal codoped Bi2O3 with ce. phase by first principles calculations. The calculation results firstly show that new impurity states appeared in band gap of alpha-Bi2O3 after single metal doping, especially for the doping of Cu, Ag and Pb, which showed shallow acceptor levels for alpha-Bi2O3. And the formation energy analysis indicates that Cu doped system was easier to be formed than other doped systems. All of those calculated properties are helpful to enhance the photocatalytic property of alpha-Bi2O3, which agrees well with experimental results. Interestingly, for anion atom N together with metallic atom (Ag, Cu, Pb, Pd, Sn) codoped alpha-Bi2O3 systems, it is found that N-2p state had impact on the electronic structure. Holes were demonstrated to be more delocalized in (Cu + N) codoped alpha-Bi2O3 system, which was responsible for high mobility of holes, then lowering the electron-hole recombination, and finally improving the photocatalytic performance of Bi2O3 significantly. (C) 2015 Elsevier B.V. All rights reserved.