To research the electronic structure and optical properties of Ga0.75Al0.25N (001) (2 x 2) and c(2 x 2) reconstruction surfaces, two reconstruction surface models are built. The band structure, density of states, work function, surface energy, and optical properties of the two reconstruction surfaces are calculated based on first principles. Results show that c(2 x 2) reconstruction surface is more stable than (2 x 2) reconstruction surface. The work functions of the two reconstruction surfaces are 3.084 eV and 3.431 eV, respectively. The band gaps of the surfaces become small compared with the bulk, which show the surfaces own metal property. The absorption coefficients of the surfaces are smaller than that of the bulk. (C) 2013 Elsevier B. V. All rights reserved.