The　SO2　poisoning　of　a　heterobimetallic　FeCu-SSZ-13　in　selective　catalytic　reduction　of　NO　with　NH3　(NH3-SCR)　was　systematically　investigated　in　this　study.　It　was　shown　that　when　SO2　is　involved　in　the　feeding　flue　gas,　the　losses　in　the　redox　ability　of　active　metals　(primary　contributor　to　deactivation)　and　in　the　number　of　Bronsted　acid　sites　both　inhibit　the　formation　of　NH4NO2　intermediate,　resulting　in　the　rapid　deactivation　of　FeCu-SSZ-13.　The　SO2　poisoning　of　FeCu-SSZ-13　at　low　temperature　is　more　serious　than　at　high　temperature,　because　of　the　more　severe　loss　of　redox　ability　of　active　metals.　Unlike　that　of　monometallic　Cu-/Fe-CHA,　the　SO(2　)poisoning　of　the　bimetallic　one　is　saliently　featured　by　that　partial　SO2　is　oxidized　to　SO3　and　partial　Bronsted　acid　sites　are　destroyed　due　to　the　formation　of　H2SO4.　This　work　may　provide　a　fundamental　understanding　on　the　SO2　poisoning　of　heterobimetallic　zeolite-based　NH3-SCR　catalysts.