Tin oxide (SnO2) microspheres with an average 2-3 μm in diameters have been successfully synthesized using SnCl4 and NaOH through a rapid hydrothermal process heated by microwave in the presence of 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF4]). Through characterization by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), thermal analysis and N2 physical adsorption, the structure of the SnO2 microspheres is proposed.