The fluorescent spectra of nanostructured Al2O3 after heat-treating at different temperatureshave been systematically investigated. The results show that for η-Al2O3 and γ-Al2O3, two broadfluorescent bands P1 and P2 appear in the wavenumber range of 20000 cm-1 to 11500 cm-1,and P1 and P2 bands are located in the wavenumber range of 20000 cm-1 to 14500 cm-1 and14500 cm-1 to 11500 cm-1, respectively The P1 band can be attributed to the impurity Cr3+luminescence. This is consistent with other author’s result for the Cr doped Al2O3. The P2band is a new fluorescent phenomenon, which has not been reported previously. In this paper,the condition of the appearance of P2 and its mechanism is discussed in detail.