Abstract: A series of cesiumsalts of 12-tungstophosphoric acid(Cs _xH_{3 -x}PW₁₂ O₄₀) were synthesized by the precipitation method and analyzed by N₂ adsorption-desorption, SEM, XRD,FT-R,and DR UV-vis.The effect of different cesium ion exchange on structure and catalytic behavior of 12-tungstophosphoric acid for the oxidation of benzaldehyde with 30% H₂O₂ was investigated.The results showed that all the sample sremained the primary Keggin structure of H₃PW₁₂O₄₀.Moreover, the particles became more uniformity and the textural parameters increased with the increase of xin Cs_xH₃-xO₄₀ .Cs₃PW₁₂ O₄₀  reached the largest surface area (109.1 m^2/and pore volume (0.121 9 cm³/g).On the other hand,Cs₃PW₁₂ O₄₀ exhibited better catalytic activities than H_3PW12 O₄₀(71%). The yield of benzoic acid was about 72% and 76% over Cs3PW 12 O 40and theothers.