Abstract: In order to save energy and reduce emission, aiming to reduce SO₂ mass concentration in flue gas emission of natural gas purification plant, using medium pressure steam as power, the liquid sulfur pool exhaust gas was pumped into Claus furnace through ejector, and the exhaust gas was preheated by low pressure steam to prevent sulfur vapor condensation. After the liquid sulfur pool exhaust gas enters Claus furnace under different loads of Claus system, the effect on reducing SO₂ mass concentration in flue gas was studied. Through the implementation and application of technical transformation, the SO₂ mass concentration in flue gas has been reduced, and the stable production of the combined plant has not been affected. It could provide a reference for similar sulfur recovery process units to reduce SO₂ emission.