By adjusting the type and proportion of doping elements in the g-C₃N₄-based photocatalyst, the internal electric field (IEF) strength of the semiconductor can be regulated. This can effectively enhance the driving force of charge separation in the photocatalytic process. It is found that the introduction of appropriate concentration of Bi and S into the skeleton structure of g-C₃N₄ can achieve efficient degradation of tetracycline (TC) and other pollutants in the liquid environment and excellent photocatalytic H₂ evolution performance (1139 μmol·L^-1·h^-1). Since the prepared samples have similar crystal structures, the relative strength of IEF can be calculated. It can be used as the basis for adjusting the IEF strength of g-C₃N₄-based semiconductor by element doping. In addition, the Bi and S co-doped g-C₃N₄ samples after solvothermal reflux show good chemical stability and can reduce the nanostructure defects caused by co-doping of heteroatoms, thus it provides a novel solution for the construction of g-C₃N₄-based dual-function photocatalyst with high activity and stability.