Safflower red and Amur Cork Tree dyes have used for dyeing on cotton fabrics largely. But they have low degree of lightfastness, So this study investigated the effect of BTCA pre-treatment on lightfastness of cotton fabrics dyed with Safflower red and Amur Cork Tree. The result is as the following; By FT-IR spectra, crosslingking was proved in cotton fabric pre treated with BTCA. K/S value of Safflower red dyed cotton fabric pretreated with BTCA was much more decreased than untreated cotton fabric with BTCA. It showed that the hue of the Safflower red dyed cotton fabric changed from reddish purple to red. However, K/S value of Amur Cork Tree dyed cotton fabric pre treated with BTCA was much more increased than untreated cotton fabric with BTCA. It showed that the hue of the Amur Cork Tree dyed cotton fabric changed from green yellow to yellow. For K/S value of Combination dyed cotton fabric pre treated with BTCA, Safflower red color was much more decreased than untreated cotton fabric. But Amur Cork Tree color was much more increased than untreated cotton fabric. It changed from reddish purple, red, yellowe red, to yellow in hue. ${{Delta}E^*}_{ab}$ of Combination dyed cotton fabric in 40 hours irradiation was 15.7, however ${{Delta}E^*}_{ab}$ of Combination dyed cotton fabric treated with 2% BTCA was 8.0, and that treated with 3% BTCA was 9.8. So, pre-treatment with BTCA to combination dyed cotton fabric with Safflower red and Amur Cork Tree showed more effective improvement of Lightfastness than untreated cotton fabric with BTCA.