Silk and ramie union fabric, DP finished with BTCA, were analyzed by FT-IR and HPLC and the physical properties were evaluated. Through FT-IR analysis, we could identify cross-linking by the presence of carbonyl peak in ramie and silk appearing at 1725 $cm^{-1}$ /. The peak intensity increased as the concentration and the temperature increased. With the use of HPLC, we could measure the amount of BTCA cross-linked using a calibration curve. The amount of BTCA detected increased in a straight line as the concentration and temperature increased. Crease resistance was higher than that of untreated silk and ramie union fabric under each processing condition and it increased in a straight line as the concentration and temperature of BTCA finishing increased.