Cu-SSZ-13 has been used as the main catalyst in selective catalytic reduction (SCR) systems for diesel because of its excellent hydrothermal stability and SCR activity. SO2poisoning is one of the main factors affecting the SCR activity of Cu-SSZ-13 at low temperatures. The effects of the actual exhaust atmosphere on the characteristics of SO2poisoning were experimentally investigated. In the absence of NH3, CuSO4species generated at Cu sites gradually increased with an increase in the SO2poisoning temperature, while the amount of H2SO4species was stable below 350 °C. The SCR NOxconversions of samples SO2poisoned at 250 °C was lower than those of samples poisoned at both 150 and 400 °C. In the presence of NH3, (NH4)2SO4species were generated, and more importantly, the production of CuSO4species was significantly promoted, which substantially reduced SCR NOxconversions for the samples poisoned at 150 and 250 °C. When the SO2poisoning temperature was 400 °C, NH3inhibited CuSO4species generation, and NOxconversions were basically unchanged. The SO2-poisoned Cu-SSZ-13 catalyst can recover most of its activity at high regeneration temperatures above 650 °C, but the regeneration temperature can be reduced to 450 °C, and all sulfate species can be decomposed while NH3is present during regeneration.