Cesium-exchanged CsxH3.0-xPW12O40 (X=2.0-3.0) heteropolyacid catalysts were prepared and applied to the decomposition of benzyl phenyl ether to aromatics. Benzyl phenyl ether was chosen as a lignin model compound for representing α-O-4 bond in lignin. Phenol, benzene, and toluene were mainly produced by the decomposition of benzyl phenyl ether. Conversion of benzyl phenyl ether and total yield for main products (phenol, benzene, and toluene) were closely related to the surface acidity of CsxH3.0-xPW12O40 (X=2.0-3.0) heteropolyacid catalyst. Conversion of benzyl phenyl ether and total yield for main products increased with increasing surface acidity of the catalyst. Among the catalysts tested, Cs2.5H0.5PW12O40 with the largest surface acidity showed the highest conversion of benzyl phenyl ether and total yield for main products.