Stable pseudo-boehmite sol was obtained by adding HNO₃ as peptizing agent and adjusting pH to be 2.0.TEM result shows that the AlOOH colloidal particle size is about 60 nm.Field emission transmission electron microscope (FETEM) result shows that pseudo-boehmite colloidal particle is composed of 8nm scaled AlOOH nanocrystals.The interaction of Eu³⁺ ions and colloidal AlOOH nanoparticle was investigated.The adsorption of Eu³⁺ ions on the surface of AlOOH nanocrystal was attributed to the chemical adsorption caused by electrostatic attraction.The photoluminescence characters of Eu³⁺ in AlOOH/Eu(NO₃)₃ composite sol system were investigated.The 529 nm emission intensity of Eu³⁺,I 592,decreased with the increase in the molar ratio of AlOOH and Eu³⁺,R_Boe/Re .The adsorption ratio (denoted R) and the adsorption density (denoted D) of Eu³⁺ ions on AlOOH colloidal particle surface was calculated from I 592 .The results show that the values of R and D increase with increasing R_Boe/Re.