The study first investigated the modification effect of natural mixed rare earths (MRE) on cobalt catalysts for CH4/CO2 reforming to synthesis gas. The Co/gamma-Al2O3 catalysts modified with the natural mixed rare earths were synthesized by the impregnation method, and characterized via ICP, BET, XRD, H-2-TPR, TEM and TG-DSC techniques. The result showed that the addition of mixed rare earths enhanced the anti-sintering ability of metallic cobalt after reduction and improved anti-coke performance of the catalysts via the synergic effect of mixed rare earths. The 20% Co/gamma-Al2O3 catalyst promoted by the appropriate natural mixed rare earths exhibited good activity and stability with low carbon formation at 800 C for 320 h reaction. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.