Abstract: PetroChina Suining Natural Gas Purification Co., Ltd. posses a large natural gas purification plant in China, which uses CPS sulfur recovery + SCOT tail gas treatment combination process, and the sulfur recovery rate is 99.8%. The mass concentration of sulfur dioxide in tail gas is below 300 mg/m³ in daily production, far below the requirement of 960 mg/m³ in the national standard GB 16297-1996 Integrated Emission Standard of Air Pollutants. In order to further reduce sulfur dioxide emission during the maintenance and shutdown process, the tail gas pipelines optimization was carried out. At the same time, the optimal method of sulfur removal by acid gas and fuel gas was explored in the case of shutdown of the same four units, and the problems in the process of shutdown were summarized. The results showed that in the stage of sulfur removal by acid gas, it was better to choose the way of removing the stage of sulfur one by one, which will not only unaffect the normal operation of the following tail gas treatment units, but also ensure the sulfur removal in each stage of the reactor more thoroughly. In the stage of sulfur removal by fuel gas, in order to fully ensure the sulfur dioxide discharge to reach standard, it was better to choose the way of removing sulfur step by step if time is permitted.