It is interesting to tune the band gap energy of SrTiO3 to harvest solar light for efficient photocatalytic hydrogen evolution. Commonly, doping is considered as promising way for band-gap engineering, due to its simplicity, effectiveness and low cost. In this theoretical research, we will demonstrate that codoping with tellurium and manganese is a promising way to alter the electronic structure and the absorption properties of SrTiO3 to increase its photocatalytic performance in the visible light range. Our results show that codoping with Se/Mn decreases the effective band gap energy of SrTiO3 by about 0.96 eV, while codoping with Te/Mn narrows significantly the band gap (by about 1.61eV), leading to an enormous absorption spectrum red-shifting. Besides, our findings show that the conduction band and valence band positions of SrTiO3 are optimized through Te/Mn codoping, in a way that makes the best use of its potential.