Fluorescence spectra of nanostructured Ａｌ2Ｏ3 bulks, which were not doped by Cr, were investigated systematically. The results show that for nanostructured samples of boehmite, η－Ａｌ2Ｏ3 and γ－Ａｌ2Ｏ3, two broad fluorescence bands (ｐ1 and ｐ2) appear, and ｐ1 and ｐ2 bands are located in the wavenumber ranges of 20000 to ～14500cm－１ and ～14500 to l1500cm－１, respectively. The ｐ1 band can be attributed to the trace impurity (Cr3+ ions) fluorescence. This is consistent with the previous results for Cr doped Ａｌ2Ｏ3. The ｐ2 band is a new fluorescence band. Finally, the stress is put on the discussion of conditions and the mechanism of the appearance of the ｐ2 band.