New photocatalysts (La³⁺-H₃PW₁₂O₄₀ and Ce³⁺-H₃PW₁₂O₄₀) were prepared, and the degradation activity of these products was evaluated. These photocatalysts were synthesized by the hydrothermal method assisted by PEG-1000 from the reactions of LaCl₃ or CeCl₃ and phosphotungstic acid. The prepared catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflection spectroscopy (UV-vis) and thermal gravimetric analysis (TGA). The catalytic activity of La³⁺-H₃PW₁₂O₄₀ and Ce³⁺-H₃PW₁₂O₄₀ was evaluated by adopting methyl orange (MO) and Rhodamine B (RhB) as model dyes, and the reaction was carried out under UV- and visible light irradiation.