Nanofluids have been demonstrated to have intriguing thermodynamic properties.In this work,we described the investigation of the phase transformation behaviors of nanofluids containing alumina(Al_2O_3)or titania (TiO_2)nanoparticles with different weight fractions.The experimental results indicate that the melting tem- peratures of nanofluids(in freezing states)are reduced with the increase of the weight fraction of nanoparticles. The reduction is related to nanoparticle species as well as nanoparticle size.