The thermodynamic parameters of La(NO3)3 and La(OH)3 are evaluated and the thermodynamics of nano-La2O3 synthetic process is analyzed. On the base of thermodynamic analysis, La2O3 nano-powders are prepared by the sol-gel method and the experiment scheme is designed by an orthogonal method. The dry-gelatin is analyzed with differential thermal analysis/thermo-gravimetric analysis (TGA-DTA) and X-ray diffraction method. The microstructure of nano-La2O3 powders is observed by transmission electron microscope. The synthetic parameters affecting the average grain size and dispersivity of nano-La2O3 particles are experimentally examined and analyzed. All the results indicate that nano-La2O3 particles well-dispersed are obtained and the average grain size is in the range of 20-50am.