The first-principle method based on the density functional theory (DFT) was used to calculate the electronic structure and optical properties of pure, N-doped, Ni-doped and Ni/N co-doped rutile TiO2 systems. The band structures, electronic density of states and spectral absorption coefficients were calculated after geometrically optimizing the above TiO2 systems. The results show that there are impurity energy levels appear within the band gaps of Ni-, N-doped systems, which provided by N-2p orbit and Ni-3d orbit; meanwhile, more complicated impurity energy levels appear within the band gaps of N/Ni co-doped rutile TiO2. The co-doped rutile TiO2 has a better optical absorption efficiency and stronger absorption cut-off wavelength red-shift. Which can be caused by the hybridization of Ni-3d orbit and N-2p orbit provides local impurity levels, so that electrons transition occurred from the valence band maximum to the impurity levels and also from the impurity levels to the bottom of conduction band, which contributes to the electron transition and enhances the absorption performance of rutile TiO2.