Ultra fine silicon-doped tin oxide composite powders have been synthesized using an advanced ultrasonic spray method. The SEM pictures revealed a particle size of about 100 nm. The structure and composition of the samples have been analyzed by XRD, FTIR, EDX and XPS. According to the XRD results, the as-prepared materials exhibit the rutile structure, with lattice parameters changing to some extent as the silicon dopant content increased. FTIR spectra showed SiO2 peaks and intensities increased in proportion to the nominal and EDX composition. XPS data were analyzed in detail and confirmed the Sn-O-Si bond exists in the composite.