Large amount of salt and alkali is usually added to dyebath in the conventional reactive dyeing of cotton due to the low substantivity of reactive dyes to cotton, hence resulting in high discharge levels of dyes as well as salt and alkali. This study intends to increase the interaction between the dye and cellulose fiber by incorporating amine groups to the fiber using a chito-oligosacchride (COS). The COS was prepared by depolymerizing a chitosan, whose degree of deacetylation is 99.3%, with sodium nitrite. With increasing COS content in the cotton fabric, the amount of salt and alkali required for the dyeing was reduced significantly and at the same time higher K/S value was obtained compared with the untreated. Also the color fastness of COS treated cotton fabric were similar to those of the untreated fabrics.