The gasification of biomass to obtain a syngas provides a competitive means for clean energy from renewable resources. The feasibility of the process depends on the performance of catalyst for upgrading of the raw fuel gas from gasifier. The highly stable NiO-MgO catalyst (Ni/(Ni +Mg)=15, atomic ratio) was prepared by co-precipitation method for the reforming of raw fuel gas. Its performance was investigated under practical conditions of biomass gasification. The Ni0.03Mg0.97O and Ni/MgO catalysts (Ni/(Ni+Mg)=15, atomic ratio) were also prepared for comparison. The NiO-MgO catalyst exhibited excellent reducibility and highly stable activity for the reforming of raw fuel gas without prereduction. No deactivation and very little carbon deposition were observed during 100 h lifetime test. The results of characterization (H-2-TPR, TGA, XRD, XPS) indicated that the formation of nickel-magnesium solid solution inhibited the sintering of nickel particles for high temperature reaction. Due to Ni2+ ions diffusion, the Ni/Mg atomic ratio decreased gradually with increasing depth. The highly stable activity was attributed to the small nickel particles size, high dispersion of nickel particles in the solid solution structure, and the promotion by catalyst reducibility. (c) 2005 Elsevier B.V. All rights reserved.