Abstract: The dissolving processes with HCl and HNO3were compared experimentally. The proportion of dissolved CeO2with HCl was less than 25% accompanied with large consumption in raw materials and serious pollution by Cl2, unsuitable for production. On the other hand, the proportion of CeO2dissolved withHNO3was over 90% in the following reaction conditions: temperature 35 to 50℃, concentration of HNO3: 7.0 to 8.5 mol/L,VH2O2:VHNO3=0.125, dissolving time: 60 min. The resolved nano-powders were homogeneous and theirgrain sizeswere in the range of 30 to 40 nm. HNO3dissolving process saves raw materials and there is no pollution, showing industrialized production.