Abstract: The acetalization of aldehydes with diols was accomplished by using ionic liquids as catalyst and reaction media.The effects of ionic liquids,reaction time, reaction temperature and reactants ratio on the conversion and selectivity of acetalization were investigated.In the reaction process removal of water produced and use of other acidic catalysts were not necessary.Medium to high conversion and good selectivity were obtained.The ionic liquid could be recycled and reused after removal of water under reduced pressure.