Abstract: Octanethiolate self-assembled monolayer-protected ld nanoparticles (C8AuNPs) were synthesized using a two-phase protocol. Au/γ-Al2O3 catalysts for low-temperature oxidation of CO were prepared by depositing C8AuNPs in hexane colloidal solution on γ-Al2O3 using“step-by-step soakage”method and by carrying out vacuum dryness and thermal treatment. For the as-prepared C8AuNPs/γ-Al2O3 catalysts, the majority of the ld nanoparticles deposited on the support was in a narrow size range of 2-3 nm. Even after 600 h of reaction, the ld particles were still in the size range of 2-4 nm. The vacuum dryness temperature affected significantly on the particle size, which increased with raising the vacuum dryness temperature. It was found from the evaluation results of catalytic performances that the 2.5%(mass fraction, w) Au/γ-Al2O3 completely converted CO to CO2 at -19 ℃ and maintained the catalytic activity at nearly 100% CO conversion for at least 900 h at 15 ℃, and the 4.0% (w) Au/γ-Al2O3 maintained the catalytic activity at nearly 100% conversion of CO for at least 2000 h in the presence of the reaction gas containing H2O at 15 ℃. Evidently, the catalyst had higher activity, od long-termstability and strong anti-moisture performance. The effect of possible factors on the catalytic activity of Au/γ-Al2O3 was studied based on the above results.