Agglomeration-free nanosized ZrO2-HfO2-Y2O3-Sc2O3 composite powders were successfully synthesized by Sol-Gel technique in heated aqueous solution of alcohol, using analytically pure ZrOCl2·8H2O, HfOCl2·8H2O, Y(NO3)3·6H2O, and Sc2O3 as raw materials. The effect of synthesis condition on the size and dispersity of the composite powders was investigated by means of XRD, TEM, and TG-DSC techniques. The results showed that well-dispersed predecessor of ZrO2-HfO2-Y2O3-Sc2O3 composite nanopowders could be obtained. The optional condition: PEG6000 as dispersant was 1%, alcohol/H2O ratio was 5/1, metallic ion concentration in whole solution was 0.5 mol·L-1 and the pH value of the solution was 12. After calcined at 620 ℃, the powder obtained was in uniform cubic structure, and its average particle size was about 13 nm, which was good for producing nanocrystalline solid electrolyte. Agglomeration-free nanosized ZrO2-HfO2-Y2O3-Sc2O3 composite powders were synthesized by Sol-Gel technique in a heated aqueous solution of alcohol, using analytically pure ZrOCl2.8H2O, HfOCl2.8H2O, Y (NO3) 3.6H2O, and Sc2O3 as raw materials. The effect of synthesis condition on the size and dispersity of the composite powders was investigated by means of XRD, TEM, and TG-DSC techniques. The results showed that well-dispersed predecessor of ZrO2-HfO2-Y2O3-Sc2O3 composite nanopowders The optional condition: PEG6000 as dispersant was 1%, alcohol / H2O ratio was 5/1, metallic ion concentration in whole solution was 0.5 mol·L-1 and the pH value of the solution was 12. After calcined at 620 ° C, the powder obtained was in uniform cubic structure, and its average particle size was about 13 nm, which was good for producing nanocrystalline solid electrolyte.