Alumina precursor sol was obtained by the reaction of Al(OC4H9)3 and acetylacetone in the solvent followed by the partial hydrolysis. This sol was measured by viscosity and the effect of pH. The powders obtained from this sol were calcined at the various temperatures. The transition of crystals and crystal state were investigated at the various temperatures. The powders dried at 90$^{circ}C$ showed amorphous and ${gamma}$-Al2O3 at 900$^{circ}C$, ${alpha}$-Al2O3 mono-phase at 1050$^{circ}C$ respectively. As a result of Al27-MASNMR analysis, amorphous and ${alpha}$-Al2O3 powders showed 6-coordinated Al, ${gamma}$-Al2O3 4-coordinated Al respectively.