Chitosan derivative (chitosan-cyanuric chloride, CHI-CNC) was prepared to improve the durability of antimicrobial activity of CD finished cotton. the reaction of chitosan with cyanuric chloride was confirmed by pH titration, elemental analysis, and FT-IR analysis. The CHI-CNC treated cotton showed an excellent and durable antimicrobial activity as compared with merely chitosan treated cotton. This is attributed to the formation of covalent bonds between the OH group of cellulose and CNC reactive group.