The 3D thermoluminescence(TL) spectra were used to study the defect structure and luminescence mechanism produced by neutron irradiation in sapphire:Mn. The TL spectra of sapphire:Mn irradiated with 1000 Gy60Co γ-rays before n eutron irradiation show a broad wavelength band around 680nm at about 350℃ which may be related to the Mn2+ ions emission, and there is the 695 nm line spectrum which superposes to 680 nm broad band that is emitted from Cr3+ ions. Comparison between the spectra of undopedα-Al2O3 crystal and that of sapphire:Mn shows that the emission spectra of undopedα-Al2O3 at 416nm at about 207℃ related to the relaxation of an electron from the excited 3P state to the ground state 1S of the F center, is seriously suppressed. After neutron irradiation with fluence 1017cm-2, new glow peaks occur at about 150℃,at wavelengths 416 nm, 680 nm and 695 nm. The intensity of the glow peak at 150℃, 695 nm is greatly enhanced compared to that before neutron irradiation. The glow peaks at wavelength 520 nm at about 150℃, 190℃ and 250℃ emitted probably from Mn2+ ions are observed after 1018cm-2 fluence neutron irradiation. This indicates that neutron irradiation produces a quite amount shallow traps and F centers, and that 3D spectra are useful for studying the trap structures and luminescence mechanism.