Alpha alumina powders have been prepared by the pyrolysis of sucrose, aluminium nitrate and ammonium nitrate. After spray pyrolysis at 400°C the mixture yields fluffy light brown precursor mass. After grinding followed by heat-treatment at 900°C and 1000°C it produced the alpha-alumina having particle sizes of 42 nm and 55 nm with surface area 12 m²/gm and 16 m²/gm respectively. The yield per unit time from precursor with ammonium nitrate is 3-4 times that of simple thermal spray pyrolysis without ammonium nitrate. The particle size and crystallite size have been decreased with increase of sucrose commensurated with ammonium nitrate in the reaction mixture. The crystallite sizes are comparable with particle sizes due to poor agglomeration due to excess addition of sucrose and ammonium nitrate.