Abstract: In order to achieve salt-free dyeing of cotton fibers with reactive dyes,the oxidized cotton fibers were obtained firstly by selective oxidation with sodium periodate.Subsequently,the HPB—NH_2 grafted oxidized cotton fibers were prepared by the reaction between the oxidized cotton fibers and the water-soluble amino-terminated hyperbranched polymer(HPB—NH_2),which was used as a grafting agent in aqueous solution.The mechanism of preparing the HPB—NH_2 grafted oxidized cotton fibers was discussed and Fourier transform infrared spectrophotometry(FT-IR) analysis indicated that all the aldehyde group of the oxidized cotton fibers have reacted with amino groups of HPB—NH_2.Reactive dyes were used to dye the HPB—NH_2 grafted oxidized cotton fabrics and their dyeing properties were tested.Results demonstrated that HPB—NH_2 grafted oxidized cotton fabrics displayed markedly enhanced color yield,and the washing fastness,rubbing fastness and leveling properties were satisfactory.