With the continuous promotion of ultra-low emission of flue gas in iron and steel industry, the integrated treatment technology consisting of circulating fluidized bed semi-dry (CFB) desulfurization technology, bag-type dust remover technology and selective catalytic reduction (SCR) denitrification technology has been gradually applied in the treatment of flue gas pollutants in sintering and pelletizing. However, in the actual operation, there are numerous unstable factors in the process equipment of the system. From the actual production, the unstable factors are analyzed in its process operation parameters and equipment operation conditions, and it is found out that flue gas parameters and equipment selection and maintenance efforts are the key factors affecting the system operation stability, and it is necessary to strengthen the operation stability of flue gas treatment system while to improve the flue gas pollutant removal efficiency by taking relevant measures such as flue gas source control and operation process control.