SnO2:Eu3+ nanoparticles were prepared by hydrothermal method. The crystal structure, size, phase composition, and morphology of the materials were investigated by X-ray diffraction measurements, scanning electron microscopy, Raman scattering spectroscopy. The absorption and optical properties of the materials were studied by UV–vis absorption spectroscopy, photoluminescence excitation spectroscopy, and photoluminescence spectroscopy. Results showed that the SnO2:Eu3+ nanoparticles had a tetragonal rutile crystal structure and were about 5–15 nm in size. They were also smaller than pure SnO2. When doping Eu3+ into SnO2, the crystal size of SnO2:Eu3+ nanoparticles decreased, the defects increased, and the crystallinity decreased. The SnO2:Eu3+ samples emitted in the emission region related to the SnO2 host and the emission peaks of the Eu3+ ion impurity. Moreover, energy transfer occurred from the SnO2 host to Eu3+ ions. The photoluminescence spectra of SnO2:Eu3+ nanoparticles with indirect and direct excitation were further studied. The influences of Eu3+ concentration on the structure, morphology, and optical properties of SnO2:Eu3+ nanoparticles were investigated in detail.