From the aspect of operation, this paper expounds the causes of flue gas SO2 not up to the standard and the technical countermeasures. EUROCLAUS sulfur recovery technology is to convert H2S and COS from acid gas produced in the low-temperature methanol washing unit into elemental sulfur. The focus of this technology is to improve the sulfur recovery rate, reduce the emission concentration of flue gas SO2, and make the emission meet the environmental requirements. The results show that the SO2 emission of flue gas is not up to standard due to the fluctuation of acid gas flow rate, improper ratio of oxygen to acid gas, improper temperature control of main combustion furnace, improper temperature control of each catalyst bed, degradation of catalyst performance, blockage of liquid sulfur pipeline, fluctuation of fuel gas-hydrogen carbon ratio, inaccurate instrument analysis and other factors. By controlling the above factors, the sulfur recovery rate is increased, and the flue gas SO2 reaches the standard and meets the requirements of environmental protection.