Al nanoparticles were prepared by flow－levitation method.The morphologies,granularities,structure and properties of particles were investigated by TEM, EDAX， XRD, UV－visible absorption spectroscopy,and thermal analysis （DSC－TG） techniques.The results show that mean granularity of the spheric Al nanoparticles is 50 nm, the maximum peak absorption appears at wavelength of 253 nm, and the oxygen percentage of Al nanoparticles is 8.2％ kept in unsealed glass bottle for half year. In Ar, the weight of Al nanoparticles increases by a factor of 20% approximately from 20 ℃ to 780 ℃, fusing peak of Al nanoparticles appears at 654.8 ℃, and melting heat is 136 J·g^-1, respectively.