After dropping Eu(NO3)3 into pseudoboehmite sol solution, europium-added pseudoboehmite xerogel was prepared by spray-drying process. Effect of Eu3 ion on pseudoboehmite phase transition and microstructure has investigated by differential thermal gravimetric analysis, powder X-ray diffraction and field emission transmission electron microscopy. The results show that phase transition temperatures of γ-Al2O3→θ-Al2O3 and θ-Al2O3→α-Al2O3 in the Eu3 -doped pseudoboehmite phase transition process are increased by 172 K and 13 K, respectively. Eu3 ions entered entirely into γ-Al2O3 or θ-Al2O3 crystal lattices, and crystallinity of γ-Al2O3 was improved, thus increasing the phase transition temperature of γ-Al2O3→θ-Al2O3. When α-Al2O3 formed in the phase transition process, Eu3 ion, which presented wholly in the form of compound EuA112O19, existed between α- Al2O3 grains. Bulk diffusion of Al3 was hindered, resulting in an increase of phase transformation temperature of θ-Al2O3→α-Al2O3 process.