The properties of the surface phonon modes in spherical SnO2 nanometer particles were studied by the method of infrared spectroscopy. The sum total of Frohlich modes of SnO2 nanometer particles were reported in our experiments. The theoretical results of surface mode frequency of SnO2 nanometer particles were presented, which agreed well with those of experiments. Finally, the effects of quantum confinement on the infrared properties of SnO2 nanometer particles were discussed.