Acid-redox bifunctional Dawson-type polyoxometalates K6P2W18O62 (P2W18) and K10P2W17O61 (P2W17) were introduced as the new-type catalysts in oxidative decomposition of lignocellulose. The lignin and hemicellulose ingredients of lignocellulose could be decomposed by P2W17 to produce diisobutyl phthalate with the selectivity of 75.67% and other aromatic and aliphatic compounds under mild conditions, evidently differed from other POMs-catalyzed lignocellulose depolymerization in which aromatic ketones and phenols were the main compounds. Diisobutyl phthalate was obtained from the oxidation of C-alpha-OR and alpha-OH of the phenyl structure. The catalyst could be recycled for three times without obvious deactivation. This is the first report of lignocellulose decomposition catalyzed by Dawson-type polyoxometalates to selectively produce phthalates.