Abstract: Selecting melamine and industrial metatitanic acid as raw materials, g-C₃N₄/TiO₂ composite was prepared by one-step heat treatment, and its phase, structure and morphology were characterized. Taking rhodamine B (RhB), methylene blue (MB) and malachite green (MG) as degradation objects, photocatalytic degradation experiments were carried out to study the effects of light, raw material ratio and initial dye concentration on the degradation of dyes by g-C₃N₄/TiO₂. Then, the mechanism of photocatalytic degradation of dyes was explored by free radical capture experiments. The results show that the visible light response range of the composites increases, and the light absorption is improved, and the composites have better photocatalytic properties. The catalytic performance of 1.0-g-C₃N₄/TiO₂ composites prepared with the mass ratio of raw materials of 1∶1, calcination temperature of 500 ℃ and calcination for 1.5 h is good. 10 mg 1.0-g-C₃N₄/TiO₂ was irradiated under the visible light of 300 W xenon lamp for 150 min, the degradation rates of MB, MG and RhB solution (10 mg/L) reach 97.20%, 96.60% and 92.72% respectively. Taking 10 mg/L MB solution as an example, after 1.0-g-C₃N₄/TiO₂ is recycled for five cycles, the degradation rate of MB still reaches 93.20%, which has the ability of multiple recycling. The main active group of 1.0-g-C₃N₄/TiO₂ for degrading MB solution under visible light was·OH, and ·O₂^- for degrading MG and RhB solution.