This manuscript describes a facile approach to modify the surface of natural cotton fibers with sulfonate groups through epoxy reaction. Sodium 1-chloro-2-hydroxylpropyl sulfonate (SCHPS) was chosen as the sulfonation agent for cotton fibers since it contains a Cl group at one end, a hydroxyl group in the adjacent position, and a sulfonate group at the other end. Epoxy was formed when it was treated with concentrated alkali. Then, the formed epoxy groups reacted with the hydroxyl groups on cellulose backbone. As the consequence, sulfonate groups were introduced over the cellulosic fiber surface. In this investigation, orthogonal experimental design was employed to study the relationships between sulfonate densities on fiber surface and the influencing variables, i.e., concentration of NaOH, molar ratio of NaOH to sulfonation agent, and duration of reaction. Under the optimal condition, up to 4.6 mmol surface sulfonate groups/100 g fiber were achieved. The resulted fibers exhibited a strong affinity to silver ions and therefore were used as the substrate of antibacterial composite of silver nanoparticles and cotton fabric which fabricated via an in situ method. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012