The pyrolysis gasoline hydrogenation unit of megaton ethylene plant at PetroChina Dushanzi Petrochemical Company was started up using high sulfur naphtha, and the sulfur content of products repeatedly exceeded the standards for a long time during the startup, greatly prolonging the startup time. The root causes of this problem were found by comparing and analyzing the system operation, catalyst performance and sulfur-containing materials in naphtha. Through the operation optimization of the revamped pyrolysis gasoline hydrogenation unit, the objectives of shortening startup time and reducing energy consumption were achieved.