The hexagonal and monoclinic GdPO 4 doped with europium ion nanocrystals were successfully synthesized by a hydrothermal method. Results show that the obtained Eu 3+ -doped GdPO 4 has a hexagonal or monoclinic structure under different synthetically process. The properties of the Eu 3+ -doped GdPO 4 nanocrystals were characterized by XRD, SEM and UV–Vis spectroscopy. A study of the photoluminescence of Eu 3+ -doped GdPO 4 has revealed that the optical properties of these nanophosphors are strongly dependent on their crystal structures and morphologies.