Abstract: Acrylic acid (AA) was grafted onto the surface of ramie fiber to get ramie-g-AA via electron beam preirradiation, then ethylenediamine (EDA) reacts with the grafted ramie fiber by preirradiation to get ramie-g-AA-EDA, and two-step amination was achieved. The monomer concentration dependence of the grafting rate and the amination rate was discussed. Through the experiments of the salt=free dyeing of modified ramie fiber, the effects of the grafting rate of AA and the rate of amination on the dyeing rate were analyzed. It is possible that AA and EDA are grafted on the ramie fiber by preirradiation, and the grafting rate of AA and the rate of amination increase with the monomer concentration respectively. When the absorbed dose is 40 kGy, and the EDA concentration is 35%, the EDA amination rate of ramie-g-AA samples (AA grafting rate is 25%) can reach 20.1%. After grafting AA, ramie fiber’s dyeing rate is reduced, and decreases with the increase of AA grafting rate, when AA grafting rate is 25.1%, the dyeing rate drops to just 4.2%. The dyeing rate of ramie-g-AA-EDA increases more significantly than that of ramie-g-AA, and increases with the amination rate, when the modified ramie fiber has a AA grafting rate of 25% and a amination rate of 25%, the dyeing rate is up to 49%.