Catalytic roles of the acid sites in Beta zeolite for the acylation of anisole (AN) with acetic anhydride were investigated. There existed obvious difference between the Beta zeolite acidity modified with inorganic alkali cation (K+) and that modified with organic base (2,4-dimethylquinoline, 2,4-DMQ). With the increase in K+ loadings, the Beta zeolite showed decreases in both total acid strength and acylation performance. Strong acid sites played the predominant role in the AN acylation. Whereas the modifier of 2,4-DMQ mainly poisoned the Bronsted acid sites and kept the Lewis acid sites almost intact. Over the Beta zeolite poisoned by 2,4-DMQ the AN conversion (X-AN) versus the concentration of Bronsted acid sites (CB) could be represented by two linear expressions, namely X-AN = 37.53C(B) - 0.20 (when 0.0053 <= C-B <= 0.0167 mmol/g) and X-AN = 2.68C(B) + 0.38 (when 0.0167 < C-B <= 0.0857 mmol/g). (C) 2013 Published by Elsevier Inc.