The electronic structures and optical properties of pure anatase TiO2, W doped, S doped and W-S co-doped anatase TiO2 are calculated using the plane-wave ultra-soft pseudo-potential (PWPP) method based on the density functional theory. The results indicate that the lattice is distorted and the lattice constant is enlarged due to doping. The doping also introduces impurity energy levels into the forbidden band. For the S-doped TiO2, its forbidden band width decreases and the introduction of impurity energy levels result in the red shift of the absorption band edge, but for the W-doped and W-S co-doped anatase TiO2, their obviously increased forbidden band gaps result in the blue shifts of the absorption spectra.