A Xe-2* excilamp (lambda = 172 nm) was applied to photo irradiate and surface modify wool fibers. The scanning electron microscopy (SEM) showed that the outer surface of the fibers was etched after excilamp treatment, and some microcracks emerged on the surface scales. X-ray photoelectron spectroscopy (XPS) analysis indicated that the excilamp-treated fibers possessed high concentration of oxygen, sulfur, and nitrogen, as well as increased hydrophilic groups, such as hydroxyl group, carboxyl group, and sulphur oxide species on the surface. Fourier transform infrared spectroscopy with attenuated total internal reflectance (FTIR-ATR) mode measurement showed that the sulphur oxide species was mainly composed of cysteic acid and S-sulphonate together with a small amount of cystine monoxide and cystine dioxide on the outer surface of excilamp-treated wool fiber. The contact angle of water on the excilamp-treated fiber decreased about 110 degrees. Using an acid dye, deeper hue was achieved in dyeing the treated fibers, evidenced by relative color strength (K/S) and brightness (L*) values. And the directional friction effect (DFE) of the wool fibers in wet obviously decreased after the excilamp treatment. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 241-246, 2010