Nanosized α-aluminum oxides have been prepared by hydrolysis of aluminum alkoxides using a sol-gel procedure. The Na(AOT) as a surface active agent was added into the alumina precursor solution to investigate the influence on size and morphology of alumina particles. The product phase was mainly boehmite with mean particle size of 20~30 nm. The crystal phases and morphology of the alumina nanoparticles were analyzed by X-ray diffractometry and by transmission electron microscopy, respectively. The TEM observations revealed that α-Al2O3 with about 80 nm spherical and hexagonal shapes was formed after calcination at 1200oC. The TG/DSC analyses were also done to determine the phase changes of alumina precursors from room temperature to 1200oC.