The SKA/CEMS-SO3-B on-line sulfur trioxide analyzer is an on-line monitoring instrument based on the special turbulence absorption and efficient capture technology, which uses spectrophotometry to automatically detect the concentration of sulfur trioxide (SO3) in the flue gas of fixed pollution sources. It can not only ensure the efficient absorption and capture of SO3 in the flue gas, but also avoid the oxidation of SO2 into SO3 during the measurement process, and reduce the measurement error. SKA/ CIMS-SO3-B on-line sulfur trioxide analyzer is suitable for on-line monitoring of SO3 concentration in the process of desulfurization, denitrification and wet electric dust removal in power plants. Reduce the corrosive effect on air preheaters and flues by automatically measuring SO3 concentration to analyze the cause and control the concentration, and reduce the blue or tan "plume" formed when flue gas is emitted.