Due to more and more strict requirements in national environmental protection, single Claus sulfur recovery process in natural gas purification plant cannot be able to meet relative requirements of tail gas emission. In order to increase total sulfur recovery, reduce the S0₂ emission concentration and meet the emission standards, a combined process of sulfur recovery and tail gas treatment is applied in certain gas purification plant. Since the combined process is applied, the gas treatment plant operates properly and S0₂ emission concentration is far below relative requirements in current and forthcoming environmental standards. Application of the autonomy-oriented tail gas treatment technology eliminate technical dependence on the international engineering companies, which has important guiding significance in saving energy & reducing pollutant emission.