Production of 5-hydroxymethylfurfural from dehydration of glucose catalyzed by 4-(3-methyl-1-imidazolio)-1-butane sulfonic acid hydrogen sulfate was studied with 1-butyl-3-methylimidazolium chloride as a solvent under microwave irradiation. The effects of catalyst dosage, reaction temperature, and reaction time on 5-hydroxymethylfurfural yields were investigated to find optimal process conditions. The yield of 5-hydroxymethylfurfural reached 43.3% at 140 degrees C for 2.5 min when the mole ratio of catalyst to glucose was 2.5:1. The ionic liquids could be recovered by extracting 5-hydroxymethylfurfural with ethyl acetate and exhibited constant activity in the recycling test.