A swelling-changeful polymer catalyst with controlled acid concentration for glycerol acetylation to biodiesel additives was carried out. This polysulfone catalyst was prepared by direct copolymerization of sulfonated monomer instead of post functionalization of polymer. The influences of acid concentration of polymer and reaction parameters (such as reaction temperature and time) on the glycerol conversion and product selectivity were studied. Glycerol conversion of 98.4% with 94.9% total selectivity of diacetin and triacetin was achieved at a moderate condition on a polysulfone catalyst with the appropriate acid concentration, which was more active than conventional Amberlyst 15 catalyst The enhanced catalytic performance of polysulfone catalyst was attributed to the stronger acid strength and better swelling property. Besides, the polymer catalyst had a changeful swelling property during glycerol esterification. It swelled at the initial reaction stage and deswelled from solution at the end of reaction, which provided a good mass transfer during the reaction and endowed easy separation of catalyst from the reaction medium after the reaction. Moreover, the polymer catalyst can be reused several times without deactivation. (C) 2015 Elsevier B.V. All rights reserved.