series of CsxH3-xPW12O40 (x=0.9-3.0) samples with regularly dependent acidity values and gradually transformed microstructures was synthesized by a precipitation method. Along with the increase in Cs content in the CsxH3-xPW12O40 samples, the concentration of acid sites decreased monotonically, and their morphologies changed gradually from compact large lumps to nano-sized particles. Mesoporous channels were formed probably because of the stacking of nanoparticles in the samples with x > 2.1. When the CsxH3-xPW12O40 samples were used as catalysts for oxidative dehydrogenation (ODH) of propane, higher conversions of propane were achieved over the catalysts with higher acidity. The formation of mesoporous structure improved propane conversion evidently. The best yield of propylene was achieved over the Cs1.5H1.5PW12O40 catalyst, which possessed a high concentration of acid sites and non-porous structure. Our studies demonstrate that not only the acidity but also the porous structure of the CsxH3-xPW12O40 play key roles in the ODH of propane. (C) 2010 Elsevier B.V. All rights reserved.