Fourier transform infrared spectroscopy(FT-IR) was used to characterize the intermolecular ester crosslinkages in cotton cellulose. The FT-IR data show that the band of the ester carbonyl group can be separated from overlapping carboxyl/carbonyl band by converting carboxyl group to carboxylate. When esterification occurs between a polycarboxylic acid and cotton cellulose, the carbonyl groups retained in the cotton exist in three forms; ester, carboxyl, and carboxylate anion. The FT-IR data were also correlated to the durable press rating result obtained. The appearance of BTCA-finished durable press silk/cotton fabrics were improved.