Carbon modified magnesium oxides (CMgO-600, CMgO-700 and CMgO-800) were prepared from pyrolyzing n-hexane vapors at 600, 700 and 800 A degrees C, respectively, on the surface of the MgO. Modification of magnesium oxide (CMgO) with carbon increased the covalent character of the Mg-O bond, consequently decreasing the basicity. TEM and H-2 chemisorption showed that the average metal particle size on CMgO was ca. 3.0 nm and the HRTEM images showed that the metal particles consisted of Pt-Sn alloys with different Pt/Sn composition. PtSn/CMgO catalysts showed much higher activity and selectivity than PtSn/MgO for the butane dehydrogenation, because a high metal dispersion on PtSn/CMgO resulted from preventing MgO dissolution during the impregnation step of metal salts on the support. The PtSn/CMgO-600 catalyst among the prepared catalysts gave the highest butenes yield.