The catalysts in the second stage reactor of the pyrolysis gasoline hydrogenation unit of PetroChina Sichuan Petrochemical Co., Ltd. was unloaded anaerobically for the first time. This paper introduces the anaerobic unloading technology, unloading process and the precautions. Safety risks such as fire, explosion, poisoning and suffocation during catalyst unloading can be effectively reduced through process handling and energy isolation, reliable gas supply system, strict control of the work environment, enhanced process monitoring, strengthened personnel training and education, and proper disposal of spent catalysts.