A series of potassium and/or phosphorus modified Co-Mo/Al2O3 FCC gasoline hydro-upgrading catalysts were prepared and the influences of potassium and/or phosphorus on the morphology, acidity and catalytic performance of the resulting catalysts were studied in the present investigation. The results showed that, compared to the single potassium or phosphorus modified catalyst, the Co-Mo-K-P/Al2O3 catalyst in which the atomic ratio of potassium to phosphorus was 2.0 could better balance the hydrodesulfurization and olefin saturation activities due to the compromised dispersion and stacking Of MoS2 Slabs on the support as well as the good acidity property, and thus present the excellent selectivity in hydrodesulfurization. The present investigation also demonstrates the superiority of adjusting the K/P atomic ratio in optimizing the structure of MoS2 slabs and thus provides a novel method for developing highly selective hydrodesulfurization catalysts. (C) 2007 Elsevier B.V. All rights reserved.