Well-dispersed quantum sized SnO₂ nanoparticles have been successfully synthesized by simple solvothermal process using ethylenediamine as both a coordination and an alkali reagent. The size of the prepared tin oxide nanoparticle has been characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) analysis. The TEM images show nano-particles as clusters with size in the range of 2.27–3.35 nm. Morphological studies were obtained by scanning electron microscopy (SEM). The optical direct band gap values of SnO₂ nanoparticles were calculated to be about 3.75–4.27eV, which were confirmed the quantum size effect. The photoluminescence (PL) properties and the possible mechanisms were also discussed.