The nano-structured alumina powder were Synthesized by the method of Low-temperature Combustion Synthesis (LCS) using aluminum nitrate and urea as raw materials, and properties of the powder were Studied by XRD, TG-DTA, FT-IR , TEM and Electron diffraction. It was found that the size of particles is about 60-80 nm averagely. The optimal synthetic conditions were obtained, i.e., the urea was the suitable fuel; the molar ratio of oxidizer to fuel was 1 : 2; the igniting temperature was 700℃. The results showed that the size of particles was effected by synthesizing temperature, the fuel and the molar ratio of oxidizer to fuel. TEM of the particles showed that the crystal habits of particle have a ball-like of structure and particles were poly-crystal by electron diffraction.