In this study, a hyperbranched chelated hydrophilic swollen-layer was constructed on the surface of polyacrylonitrile (PAN) fiber with amino trimethylene phosphoric acid (ATMP) as a terminal group, which applied as an adsorbent for seawater uranium U(VI) extraction. This shows that U(VI) enter the gel-like swollen-layer to form a more complex body structure. The molecular chain conformational extension in the swollen-layer reduces the resistance of the uranyl ion to enter the swollen-layer, which is conducive to the adsorption behavior. The adsorption performance on the U(VI) by the adsorption experiment were found to be consistent with the Langmuir isotherm adsorption model and the pseudo-second-order kinetics, indicating that the adsorption of U(VI) by this material is uniform single-layer chemical adsorption. Ion competition experiments and cyclic adsorption experiments verify the practical application potential of the materials. In the dynamic simulation of seawater adsorption experiments, the adsorption capacity of the adsorbent reached 7.4 mg/g. Studies on the adsorption mechanism have found that a large number of hydroxyl groups in the swollen-layer and ATMP as an end machine have a chelation effect on U(VI). (C) 2020 Published by Elsevier Inc.