Abstract: With the increasingly stringent requirements of the state on environmental quality, GB 39728-2020 Emission Standard of Air Pollutants for Onshore Oil and Gas Exploitation Industry was officially issued by the Ministry of Ecological Environment of the People's Republic of China, which specifies that the control index of SO₂ mass concentration in tail gas from small and medium-sized natural gas purification plants (sulfur output less than 200 t/d) is 800 mg/m³. In order to meet the standard, the tail gas treatment process should be reformed. The technical and economic comparison of tail gas treatment process which are suitable for small and medium scale natural gas purification plants was carried out. For medium scale (sulfur output of 10-200 t/d) sulfur recovery units, oxidation absorption process was recommended. For small scale (sulfur output less than 10 t/d) sulfur recovery units, liquid-phase oxidation-reduction process was recommended.