The electronic structure and magnetism in Co14Ti2O14 systems are investigated by using the first-principles calculations. The system of 2 x 2 x 2 Co14Ti2O16 supercell doped with Ti at 9 and 11 position shows a half-metallic character with a high spin polarization. Based on the above system, we remove two O atoms to form two O vacancies. The two O vacancies near Ti have a huge effect on the electronic structure and magnetic properties of Co14Ti2O14 system. When O vacancies locate at 1 and 3 positions, the system shows a half-metallic character. For the O vacancies at 6 and 8 positions, the system shows a semiconducting character. The system with O vacancies at 9 and 11 positions is a typical spin gapless semiconductor. (C) 2015 Elsevier B.V. All rights reserved. 2