Nickel　production　is　a　typical　multi-element　symbiotic　smelting　process,　and　inventory　allocation　is　an　important　technical　factor　that　restricts　the　accuracy　of　its　life　cycle　assessment.　In　this　study,　the　flash　furnace　smelting　process　of　nickel　sulfide　ore　with　the　most　intensive　symbiotic　reaction　was　taken　as　the　research　object,　and　various　inventory　allocation　methods　such　as　system　boundary　extension,　physical　relationship　and　mass　allocation　were　adopted　to　allocate　CO2　emissions　among　the　three　elements　of　Ni,　Cu　and　S.　The　allocation　calculation　results　by　system　boundary　extension　show　that　the　allocation　factor　of　non-metallic　symbiotic　elements　is　29.　86%,　and　the　allocation　factor　of　metal　symbiotic　elements　is　70.　14%　.　The　results　show　that　the　system　boundary　extension　method　is　not　suitable　for　intermediate　products.　The　factor　of　physical　relationship　allocation　are　accurate,　but　need　to　be　supported　by　a　large　number　of　process　parameters.　The　mass　allocation　is　easy　to　calculate,　however,　its　accuracy　depends　on　the　differences　of　physical　and　chemical　properties　between　symbiotic　products.　©　2024　Beijing　University　of　Technology.　All　rights　reserved.