Alumina gel was prepared by the hydrolysis of aluminum isopropoxide Al(OC3H7i)3 at low temperature. Sample were calcined at the various temperatures for 10 houres in the electric furnace, respectively. In order to investigate the various propertis-thermal properties, pore size and distribution, and the transition of crystals, infrared spectroscopy, thermal analysis, particle size analysis, scanning electron microscopy, and porosimetry were employed. Transparent alumina gel was opalized at 1200$^{circ}C$. Porosity was about 87% with pores below 0.7$mu extrm{m}$ and 55% at 1200$^{circ}C$. The gel was transformed along the rising of temperature as follows; Boehmitelongrightarrow$delta$-Al2O3longrightarrow$ heta$longrightarrowAl2O3longrightarrow${alpha}$-Al2O3.