A new sol-gel route was applied to prepare alumina films by using AlCl3. 6H(2)O as starting material and acetylacetone (AcAc) as additive. Our research results show that AcAc and aluminum form a complex compound in the sol, which makes the sol very stable. Meanwhile, the complex structure prevents the decomposition going on quickly during the sintering process and the obtained films are free of cracks. The as-prepared films were amorphous. When the sintering temperature reached up to 600 degrees C, gamma-Al2O3 began to form and was transformed to alpha-Al2O3 at temperatures over 1200 degrees C.