A double polyoxometalates?based composite catalyst material was prepared by Mechanochemistry. In order to compare with the double polyoxometalates?based composite catalyst material, one polyoxometalates?based were prepared by the same method. The structures of these catalysts were characterized by X?ray powder diffraction, Fourier transform infrared spectroscopy, and liquid ultraviolet spectroscopy. The photocatalytic degradation of rhodamine B (RhB) was selected as a model reaction to evaluate its photocatalytic activity and the possible mechanism were further explored in the degradation process. The results indicate that the degradation efficiency of H₃PMo₁₂O₄₀&H₄SiW₁₂O₄₀@MOF?199 is 92% while irradiating in simulated sunlight for 60 minutes, which is superior to that of the corresponding single POMs catalysts H₃PMo₁₂O₄₀ or H₄SiW₁₂O₄₀@MOF?199 and has a good cycling activity. The synergistic effect of the good photocatalytic activity of polyoxotungstates and the good oxidation?reduction ability of polyoxomolybdates, which provides a new vision for designing diverse POMs@MOFs composite catalysts with different catalytic properties.