A series of NiMg(Ca)(b)AlcOx catalysts prepared by co-precipitation were investigated for carbon dioxide reforming of methane at 750 degrees C and one atmosphere to determine the mechanism of these catalysts' activity. X-ray diffraction, scanning electron microscopy combined with energy dispersive X-ray analysis and temperature programmed reduction showed that Ni-Mg-Al-O solid solution formed in the catalysts. NiMg3AlOx exhibited excellent performance with a stable CH4 conversion rate of 3.3854 x 10 (3) (mol/g cat/s), due to the formation of Ni-Mg-Al-O solid solution with a high proportion of Ni-Mg-O, and an optimum proportion of weak to intermediate to strong basic sites. Changing the Mg/Al atomic ratio of NiMgbAlcOx affects these catalysts' performance. Replacing Mg in NiMg3AlOx with Ca obviously reduces catalyst activity and stability, because of a lack of Ni-Mg solid solution and a smaller Brunauer-Emmett-Teller specific surface area. (C) 2012 Elsevier Ltd. All rights reserved.