The influence of high-temperature annealing (900-1700 оС) on the morphological features, luminescent and dosimetric properties of ultrafine α-Al2O3 ceramics obtained from nanopowder by its compaction has been studied. In contrast to previously published papers, for more reliable and unambiguous determining of the relationship between the nanocrystallite size and luminescent properties, the samples were annealed in air without a reducing agent. It has been established that at Т>1500 оС there is a significant increase in the intensity of thermoluminescence (TL) of the peak at 170 оС, which coincides with the temperature range of the most significant increase in the size of nanocrystallite. Another reason for the increase in the TL response may be the formation of luminescence centers during annealing, which is proved by the appearance of a new cathodoluminescence band at 2.2–3.4 eV of unknown nature. The analysis of the dose dependences of TL of nanostructured ceramics irradiated with a high-dose pulsed electron beam (130 keV, 1.5 kGy per pulse) reveals their sublinear nature. Moreover, anomalous TL fading has been found, the magnitude of which increases with a crystallite size.