SF6　is　widely　used　in　circuit　breakers　for　rated　voltage　of　40.5kV　and　above　due　to　its　excellent　insulation　and　arc-quenching　performance.　Decomposed　components　analysis　(DCA)　method　is　considered　one　of　the　most　promising　methods　for　the　condition　monitoring　and　fault　diagnosis　of　SF6　circuit　breaker.　The　arcing　contacts　must　be　eroded　by　high　temperature　electric　arc　when　the　circuit　breaker　interrupts　current,　which　has　a　significant　influence　on　SF6　decomposition　products.　In　this　paper,　the　influence　of　arcing　contacts　erosion　on　SF6　decomposition　products　was　studied.　The　experiments　were　carried　out　on　a　40.5kV　SF6　circuit　breaker.　The　gas　chromatograph　and　electrochemical　sensor　were　used　to　analysis　the　decomposition　products.　It　has　been　found　that　the　concentration　of　decomposition　products　increases　with　the　arc　energy.　The　arcing　contacts　erosion　has　a　significant　effect　on　the　concentration　of　SO2,　SOF2,　CO2　and　CS2.　Comparing　with　the　state　before　contacts　erosion,　the　concentration　of　SO2+SOF2　has　decreased　significantly.　The　concentration　of　CS2　has　increased,　and　the　concentration　of　CO2　has　increased　rapidly.　The　main　reason　for　the　change　of　decomposition　products　concentration　before　and　after　contacts　erosion　is　discussed.　The　research　results　can　provide　the　effective　basis　for　the　condition　evaluation　and　fault　diagnosis　of　SF6　circuit　breakers.　©　2019　IEEE.