Abstract: Core-shell nanometer TiO₂/Al₂O₃ particles were prepared by one-step hydrothermal method. The optimized reaction parameters were as follows:the precursor's pH about 9. 0, hydrothermal temperature of 200℃ and hydrothermal reaction for 3 hs. The average particle size of the product was about 20 nm. The nanometer TiO₂/Al₂O₃ particles prepared by one-step hydrothermal are well coated. Furthermore, all of Al_2p、Ti_2p, O_1s in the composite powder's surface have taken place chemical displacements when compared with standard binding energy. This indicates that chemical bond of Al-O-Ti has been formed.