A novel Ultrasonic Assisted Membrane Reduction (UAMR)-hydrothermal method was used to prepare flower-like Pt/CeO₂ catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO₂ catalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), N₂ adsorption, and hydrogen temperature programmed reduction (H₂-TPR) techniques. The catalytic performance of the catalysts for treating automobile emission was studied relative to samples prepared by the conventional wetness impregnation method. The Pt/CeO₂ catalysts fabricated by this novel method showed high specific surface area and metal dispersion, excellent three-way catalytic activity, and good thermal stability. The strong interaction between the Pt nanoparticles and CeO₂ improved the thermal stability. The Ce⁴⁺ ions were incorporated into the surfactant chains and the Pt nanoparticles were stabilized through an exchange reaction of the surface hydroxyl groups. The SEM results demonstrated that the Pt/CeO₂ catalysts had a typical three-dimensional (3D) hierarchical porous structure, which was favorable for surface reaction and enhanced the exposure degree of the Pt nanoparticles. In brief, the flower-like Pt/CeO₂ catalysts prepared by UAMR-hydrothermal method exhibited a higher Pt metal dispersion, smaller particle size, better three-way catalytic activity, and improved thermal stability versus conventional materials.