Neutron-irradiation induced defects formation and optical properties change in sapphire (α-Al2O3) are discussed. Czochralski (CZ) and temperature gradient technique (TGT) grown sapphire crystals are irradiated by neutrons, and F, F+ and F+2 color centers are formed in both crystals according to absorption and fluorescence spectra. But the concentration of color centers is different. Concentration of F+ center in TGT crystals is higher than that in CZ samples, while the F center concentration in CZ crystals is higher than that in TGT crystal. It is attributed to different impurities concentration of sapphire samples. Obvious thermoluminescence peaks at 145 ℃ and 150 ℃ are found in CZ and TGT grown sapphire crystals respectively. With calculation by initial elevation method, thermoluminescence trap depths of two crystal samples are 1.15 eV and 1.05 eV, respectively.