Nano fluorescent powder of Y4Al2O9:Eu3+ was synthesized by sol-gel method.The XRD shows that the product prepared at 900℃ is pure-phase Y4Al2O9:Eu3+.The Y4Al2O9 powder is nano-size crystal testified by BF and ED analysis of TEM.The grain diameter of Y4Al2O9 is in the range between 20 and 50nm,and its average is 30nm.The luminescent spectra show that Eu3+ ious occupy two kinds of sites in Y4Al2O9 crystal lattice.One is in the strict inversion center,and the other is in off lying inversion center.When excited with UV light (λ=254nm),Y4Al2O9:Eu3+ exhibits an orange emission band at λ=590nm due to the 5D0→7F1 transition and a red emission band at λ=610nm due to 5D0→7F2 transition.