PetroChina Dushanzi Petrochemical Company has increased the processing proportion of Mahu crude oil. Due to the high arsenic content of Mahu crude oil, the arsenic content of the naphtha produced exceeded the standard, leading to risks such as the poisoning of catalysts for and gasoline hydrogenation reactors in the ethylene plant, the shortening of catalyst life and the poor quality of hydrogenation products. The arsenic removal system was not allowed to be put into use because there were some non-compliance problems and operational safety risks, so local modification was required for the existing arsenic removal process and the environmental non-compliance. After the modified arsenic removal system was put into use, it was operated in compliance with relevant standards, and good arsenic removal effect was achieved.