Cotton, which has abundant oxygen-containing hydrophilic groups, can adsorb a lot of water or other water soluble materials. In this paper, cotton was impregnated in CoCl2 aqueous solution. Co2+ can be uniformly adsorbed on cotton fibers. After been freeze-dried, the Co2+-adsorbed cotton was carbonized under an inert atmosphere and the Co nano-particles (NPs) modified cotton derived carbon fibers (Co/CCF) were obtained. The Co/CCF was then dispersed in RuCl3 aqueous solution, so that Ru3+ can be reduced by metallic Co NPs through spontaneous replacement reaction and covered on Co NPs surface. Hence, the Ru@Co/CCF catalyst was prepared with low Ru loading in the view of Ru saving. In the catalytic hydrolysis of ammonia borane (NH3 center dot BH3, AB), the Ru@Co/CCF catalyst showed excellent catalytic activity as compared with Ru/CCF and many other noble metal based catalysts. The superior activity of the catalyst is mainly due to the highly dispersed Ru@Co NPs on the carbon fibers and the uniform covering of the metallic Ru on the surface of Co NPs. Moreover, owing to the magnetic core of the Ru@Co NPs, Ru@Co/CCF catalyst can be easily separated from the reaction system using an external magnetic field. Thus, this work provided a useful strategy for facile preparation of low precious metals loading catalysts using cheap and environmental starting material as catalyst support precursor material. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.