In this research, nanometer TiO2-Al2O3 Composite powders were synthesized by the gas-phase oxidation of TiCl4 and AlCl3 in a high temperature tubular aerosol flow reactor. The measurement of EDS, XPS, XRD and TEM were used to characterize the chemical composition, crystal structure, and size of the particles. The crystal structure of titania and alumina in composite particles was affected by the AlO3 and TiCl4 feed ratio. Aluminum titanate was formed when residence time was 1.73 s, reaction temperature was 1400 degreesC, and AlCl3 and TiCl4 feed ratio was 2.80. The effect of processing parameters on the particle size and distribution of composite particles was studied. As the preheating temperature of oxygen increased, average particle size of the composite particles became smaller and size distribution more uniform. Enhancement of flow rate of cooling gas injected into reactor tail was benefit controlling the particle size. The composite particle size increased, respectively, with increasing reaction temperature and residence time.