Chain-like Ru nanoparticle arrays, 1-3 mn in diameter and similar to 280 nm in length, have been synthesized by reducing the complex of Ru ions with poly(N-vinyl-2-pyrrolidone) (PVP) by 1 MPa H-2, at 353 K, in aqueous media. The morphology of these Ru nanoparticle arrays could be varied from long chain-like to cross-linked arrays by adjusting the reaction conditions including the average molecular weight of PVP and the mole ratio of repeat unit of PVP to Ru. The whole formation process is supposed on the basis of their TEM and TG studies. The obtained chain-like Ru nanoparticle arrays show high activity in hydrogenation of phenol with broad concentration, ranging from 10 to 10,000 mg l(-1) at 353 K, under 1 MPa H-2, in aqueous media. (C) 2007 Elsevier B.V. All rights reserved.