Nano-crystalline boehmite (AlOOH) proposed as a precursor for g-Al2O3 production was prepared using precipitation process. The mixture of two starting solutions of AlN3O9.9H2O and Na2Al2O4 was formed and NaOH was used as pH adjustment. Various preparation conditions, starting pH and temperatures were applied. The results suggested that high purity AlOOH powder could be obtained at solution temperature above 60oC and starting pH was in range 7-11. Their crystalline size increased from 2.4 to 3.9 nm with increasing pH. According to the results, AlOOH from pH 8 and temperature 80oC was selected for producing the g-Al2O3 by calcination in the temperature range of 350oC-1100oC. Transformation from AlO(OH) to g-Al2O3 could be readily observed from the whole temperature range and g-Al2O3 crystalline size was increased with increasing calcination temperature. After the temperature reached 1100oC, transformation to a- and q- phases were also found. Morphology of g-Al2O3 powder shows a strong aggomeration.