Tri-methylammonium-butane sulfonate (TMBSA) ionic liquid (IL) catalyzed efficiently acetylation of acetic anhydride with various alcohols, hydroxyesters and phenols, under solvent-free conditions was described as a novel method. [TMBSA][HSO4] ionic liquid (1.0 mol%) is able to promote quantitative acetylation at low temperature, in high conversion and selectivity (>= 95%). The process is highly effective, environmentally benign, and very selective. Furthermore, [TMBSA][HSO4] ionic liquid was conveniently separated with the products and easily recycled to catalyze acetylation reaction again with excellent yields.