Nanocrystalline Al2 O3 Phosphor has been synthesized by the chemical Method. Annealed at different Temperature (800, 1000, 1200, 1400 1600 o C) the synthesized sample is annealed at a high temperature of 1600 o C. Phase change from α- Al2 O3 : C To γ- Al2 O3 : C is Observed due to annealing. These nanocrystalline samples were irradiated with gamma radiation their Thermoluminescence, characteristics have been studied. The TL glow curve is the single peak at 185 C and Large increase in TL and OSC Sensitivity. TL responses have been studied with the gamma radiation. For dose varying from 100Gy.The XRD of Al2 O3 Phosphor Annealed At 800 o C and SEM Al2 O3 Phosphor annealed at 1200 o C, Thermoluminescence Glow Curves of Al2 O3 Phosphor Annealed at Different Temperature.