Spin-polarized density functional theory calculations were performed to investigate the magnetism of bulk and Cu2O surfaces. It is found that bulk Cu2O, Cu/O-terminated Cu2O(111) and (110) surfaces have no magnetic moment, while, the O-terminated Cu2O(100) and polar O-terminated Cu2O(111) surfaces have magnetism. For low index surfaces with cation and anion vacancy, we only found that the Cu vacancy on the Cu2O(110) Cu/O-terminated surface can induce magnetism. For atomic and molecular oxygen adsorption on the low index surfaces, we found that atomic and molecular oxygen adsorption on the Cuterminated Cu2O(110) surface is much stronger than on the Cu/O-terminated Cu2O(111) and Cuterminated Cu2O(100) surfaces. More interesting, O and O-2 adsorption on the surface of Cu/O terminated Cu2O(111) and O-2 adsorption on the Cu-terminated Cu2O(110) surface can induce weak ferromagnetism. In addition, we analysis origin of Cu2O surfaces with magnetism from density of state, the surface ferromagnetism possibly due to the increased 2p-3d hybridization of surface Cu and O atoms. This is radically different from other systems previously known to exhibit point defect ferromagnetism, warranting a closer look at the phenomenon. (C) 2015 Elsevier B.V. All rights reserved.