The synthesis of sodium tungsten oxides (NaWO3) particles was accomplished to apply on the heat shielding film. In this preparation, Taguchi method with L-9 orthogonal array was used to optimize experimental conditions for the formation of NaWO3 particles. Primary mean particle size and the standard deviation of NaWO3 particles were considered as the characteristics. Concentration of sodium tungstate (Na2WO4), concentration of sodium borohydride (NaBH4), and pH value were selected as main parameters. As the result of Taguchi analysis in this work, the concentration of sodium tungstate was the most influencing parameter on the particle size and the standard deviation. The pH value had also principal effect on particle size and size distribution. The optimal conditions were determined by using Taguchi optimization design method and NaWO3 particles with primary mean size (similar to 100 nm) were prepared. By the analyses of X-ray diffraction and UV-vis spectrum, it was found that the annealed NaWO3 particles were more effective on heat shielding than non-annealed particles. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.