A highly active assembled Pt/TiO2 catalyst (Pt/TiO2-AS) was synthesized using a simple directadsorption method, in which uniformly dispersed Pt nanoparticles were directly loaded on a TiO2 support. Compared with Pt/TiO2 produced by wet impregnation (Pt/TiO2-WI), the Pt/TiO2-AS catalyst exhibited higher activity in the total oxidation of toluene, with a toluene conversion to CO2 and H2O of 100% at 150°C. The high activity remained even at high toluene concentrations and gas hourly space velocities. The properties of the synthesized catalysts were characterized using X-ray diffraction (XRD), N2 adsorption-desorption (Brunauer-Emmett-Teller (BET) method), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of H2 (H2-TPR), and Fourier-transform infrared (FTIR) spectroscopy. The results showed that the Pt/TiO2-AS crystallites were smaller than those of Pt/TiO2-WI, with fine dispersion, greater Pt 0 exposure on the support surface, and more active Ti-O bands, giving more oxygen vacancies and reactive oxygen species. The valence states of the active centers changed significantly (Pt 0 →Pt δ +) during stability tests; this is the main reason for the deactivation of the Pt/TiO2-AS catalyst.