The thermal performances of nano TiO2 and ZrO2 partcles modified with stearic acid have been investigated by means of DSC and TGA. The results obtained, combined with the result of TEM analysis, show that the surfaces of nano TiO2 and ZrO2 particles are mded modified by stearic acid. The rise of melting points of the surface modified layers is caused by the existence of the nano particle nuclei. Besides. as the temperature rises to about 710 K,adhesion and crystal transformation in the nano particles occur due to their big specific surface area and unstable crystal structure.