Core-shell Au@TiO2 nanoparticles with truncated wedge-shaped TiO2 morphology have been synthesized successfully by a simple and flexible hydrothermal route. Morphological evolution of TiO2 shells was investigated by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction technique. It has been revealed that the truncated wedge-shaped TiO2 shells experience an epitaxially segmented orientation growth. Also, the (101) crystal planes of TiO2 crystals grow preferentially on the surface of gold nanocrystals stabilizing the heterointerfaces, then faster [001] growth results in the "budding" process occurs, producing growth sites on the initial deposition TiO2 layers, where the TiO2 crystals grow up into truncated wedge-shaped morphologies. It is also found that morphological evolution of TiO2 shells is dependent on the produced F- ion concentration from hydrolyzed TiF4 precursors. The produced F- ions not only facilitate the formation of well-defined wedge-like TiO2 shells, but also contribute to the externally exposed truncated crystal {004} facets. As the representative photocatalyst, the catalytic activities of the resultant core-shell Au@TiO2 nanoparticles were investigated by photoinitiated oxidation degradation of gaseous acetaldehyde. It has been indicated that the nanostructured core-shell Au@TiO2 photocatalyst represents high photocatalytic activity when exposed to UV or visible light irradiation. The high phototocatalytic performance is also largely attributed to the preferentially grown TiO2 shell structures and metal (Au)-TiO2 heterointerfaces.