Aromatic polycarboxylic acids can directly react with cellulose to form ester cross-linking Structures and provide wrinkle resistance functions to cotton fabrics, different from aliphatic polycarboxylic acids, which will form anhydrides as intermediates. Sodium hypophosphite is a catalyst proven effective in the reactions of both acids. In order to find alternative catalysts, the mechanism of the direct esterification and the role of the catalyst in the reaction were investigated in this study. Several sodium salts of phosphorous acid and dichloroacetic acid with varied plc values were employed in the treatment of cotton fabric with 3,3',4,4'-benzophenone tetracarboxylic acid (BPTCA). The results confirmed that the overall reaction follows the Fischer esterification mechanism, an acid catalyzed reaction. The acid anions also play an important role in the reaction. Results of wrinkle recovery angles, FTIR band ratios of ester bonds, and thermogravimetric analyses of the treated fabrics consistently supported the mechanism.