By using the first principles based on the density functional theory and the general gradient approximation method, the electronic structures and optical properties of N, Co single-doped and N-Co co-doped anatase TiO2 are studied, and the effects of two kinds of different substitutions where the O site replaced by N are explored. The study results show that the impurity energy levels of both N and Co single-doped anatase TiO2 appear within the band gaps, and as for N-Co co-doped anatase TiO2,the more complicated impurity energy levels appear within the band gaps. The band gaps of the doped anatase TiO2 become narrower. Compared with that of the N, Co single-doped anatase TiO2, the stability of the co-doped anatase TiO2 is better, the optical absorption efficiency in the visible light region improves obviously and the absorption spectral redshift is more obvious. Compared with the type 1, the type 2 of co-doped anatase TiO2 has a higher absorptivity in the visible light region and a wider absorption spectral redshift range.