In this investigation, a mesoporous gamma-Al2O3 with large surface area and good thermal stability was synthesized and employed as the support for preparing a series of Pd-Pt nanocrystalline catalysts by using a high-temperature solution-phase reduction method. The PdOx (x = 0, 1) and PtOx (x = 0, 2) nanoparticles were found to have a small diameter(about 2 nm) and were highly dispersed on the surface of the mesoporous gamma-Al2O3. The results show that catalysts with the appropriate ceria greatly improved the physical adsorption/chemisorption of benzene to Pd-Pt nanocrystals, which greatly enhanced the activity to achieve the complete oxidation of benzene. The high activity of the catalyst was mainly due to the nano-effects of Pd-Pt nanocrystals and the interactions among the active components. 0.2% Pd-Pt(1:1)/10% Ce/gamma-Al2O3 demonstrated the best activity for the complete oxidation of benzene at 200 degrees C. Furthermore, this catalyst maintained 95% benzene conversion for 1000 h at 190 degrees C and displayed good resistance to water and Cl-poisoning, which indicated that the Pd-Pt nanocrystalline catalysts have promise for adoption by the industry.