Ni-B alloy is a novel industrial catalyst famous for its high activity, low-cost, and strong sulfur resistance in hydrogenation reactions. To get an insight into the special properties of Ni-B alloy catalyst, the adsorption of sulfur on NimB2 (m = 1-4) clusters has been studied with the density functional theory (DFT) method. The theoretical results show that the adsorbed sulfur tends to be connected with boron, not with nickel in the Ni-B alloy catalyst. This adsorption site prevents active nickel from being poisoned by sulfur or even being oxidized in the practical catalytic processes. This provides a sound explanation for the strong sulfur resistance of Ni-B alloy in the catalytic hydrogenation reactions. (C) 2002 Elsevier Science B.V. All rights reserved.