Abstract The preparation of tellurium dioxide (TeO 2) nanoparticles in a mild condition had been studied. The acid medium, such as gallic acid or acetum was used to prepare the TeO 2 nanoparticles at room temperature. The functions of acids were investigated by Nano-ZS, TEM, SEM, FTIR, Raman spectra and XRD. The results showed that the modification and modulation of gallic acid on the TeO 2 nanoparticles were stronger than that of acetum. The TeO 2 nanoparticles prepared in gallic acid were the orthorhombic phase β-TeO 2 spheres in the range of 30–200 nm. The TeO 2 nanoparticles prepared in acetum were the tetragonal phase α-TeO 2 irregular flakes in the range of 40–400 nm.