High-purity and homogeneous powders of CeB6 with nanometer size were prepared by combustion synthesis and subsequent acid- leaching. The effects of reactant ratio on the phase and morphology of the combustion product were discussed. The combustion product and leached product were analyzed by XRD, SEM and EDS. The results indicate that the combustion product consists of CeB6, MgO and Mg3B2O6. The combustion products are denser and less layered when the Mg content and KClO3 content increase. The content of CeB6 in the combustion product could be enhanced with increasing the excessive content of Mg. The purity of CeB6 is higher than 99.0% and its particles are smaller than 150nm.