Abstract: The running status of tail gas standard lifting part of large scale sulfur recovery plant and the characteristics of the desulfurization process of CTS complex iron were introduced. The problems of sulfur accumulation in the packing layer of desulfurization reactor, the efficiency of filter press and the quality control of circulating solution in the actual production of exhaust gas standard raising unit were described, and the causes were analyzed in detail. The problem of sulfur accumulation in the packing layer was completely solved in the non-shutdown state by adding additional desulfurization reactors, replacing fillers and increasing the circulating rates of solution. The pressure drop of some reactor fillers in tail gas standards was within a reasonable range, and SO₂ mass concentration in tail gas emission≤10 mg/m³, which was far below the latest environmental protection national standards. The experience could provide reference for the technical transformation of similar devices.