Phosphotungstic acid (HPWA) has been introduced into the mesoporous molecule sieve SBA-15 by a sol-gel technique. The samples were characterized by XRD, BET, FT-IR, XRF and NH3-TPD. The effects of the polar solvent on the hydrothermal stability have been comprehensively studied by washing the samples with an EtOH/H2O mixture and conducting esterification involving polar solvents. Although the acid amount of the fresh impregnated catalyst was superior to the sol-gel counterpart, the sol-gel derived composite is more stable in the acidic property and the structural regularity of the mesoporous material than the impregnated sample. Catalysis tests including reusability of the samples also prove that the sol-gel derived composite is more suitable for the use for heterogeneous catalysis. (C) 2004 Elsevier B.V. All rights reserved.