Abstract: The application situation of FF-66/FC-52 combined catalysts developed by FRIPP in the 1.5 million t/a diesel oil hydrogenation upgrading unit of PetroChina Karamay Petrochemical Co., Ltd.is analyzed.Practical industrial application of the combined catalysts shows that the mass contents of sulfur and nitrogen in product diesel are both less than 2.0 μg·g-1, naphtha yield increases from 14.5% to 32.9%, product diesel yield decreases from 50.9% to 39.4%, and the yield ratio of diesel-gasoline decreases from 3.22 to 1.20 under the conditions that reaction pressure is 11.5 MPa, average temperature of refining reactor is at 360℃, and average temperature of cracking reactor is at 369℃.FF-66/FC-52 catalysts have excellent hydrodesulfurization and denitrification activities, and high naphtha product selectivity.The successful application of catalyst grading system can provide a certain reference for formulating schemes to upgrade oil quality and reduce diesel-gas ratio for similar units.