Owing to the great harm that water pollution has caused to the natural environment, the effective treatment of sewage is crucial. In this study, Sm-TiO 2 /g-C 3 N 4 composites were synthesized for the degradation of MB and TC pollutants. The experimental results showed that up to 91.8% and 93.3% of MB and TC pollutants were removed within 120 min of illumination, which were 2.8 and 2.3 times greater than that of pure TiO 2 , respectively, showing the good optical properties of the composites. Due to the coupling between Sm-TiO 2 and g-C 3 N 4 , the separation of photogenerated electron holes is accelerated, thereby enhancing the photocatalytic activity of the composites. This not only enabled the strong redox ability of TiO 2 to be retained, but also effectively promoted electron migration, thus improving the photocatalytic activity of the composites.