In this paper, TiO2/g-C3N4 composite powder was prepared by electrostatic adsorption method, and its morphology, composition and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectometry (UV-Vis DRS) and other characterization methods. Rhodamine B was used as a simulated pollutant to characterize its photocatalytic performance under UV light. The result show that: in the Rhodamine B degradation experiment, when the loading amount of TiO2 reaches 15% (mass fraction), the composite powder has more obvious catalytic degradation effect, and the degradation efficiency can reach 99.40% within 20 min. After adding isopropanol as hydroxyl radical capture agent, the degradation rate decreases to 27.30%, and it is determined that the main active substance of the reaction is hydroxyl radical. Ultraviolet assisted Fenton reaction can obviously improve the effect of traditional Fenton reaction, and the reaction mechanism of catalyst was explored.