The synthesis of dimethyl carbonate (DMC) was investigated through the transesterification of ethylene carbonate (EC) with methanol using quaternary ammonium salt catalysts (QX). The reaction was carried out in an autoclave at 120-140℃ under carbon dioxide pressure of 250-400 psig. The main by-product was ethylene glycol (EG). The quaternary salts of larger alkyl group, and more nucleophilic and more basic counter anion exhibited higher catalytic activity. TBAC showed 73.2 % of EC conversion with 60.6% DMC yield at 140℃ with MeOH/EC ratio of 8.Kinetic studies are also performed to better understand the reaction mechanism.