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.