Abstract: In order to systematically calculate the carbon emission of assembled steel structure office building, this paper constructs a full life cycle carbon emission calculation model of assembled steel structure, provides a clear calculation method with the help of Autodesk Revit, Tekla Structures and DeST-C, and carries out a full life cycle carbon emission calculation in accordance with the "Standard for the Calculation of Carbon Emission from Buildings" (GB/ T51366-2019), the whole life cycle carbon emission calculation was carried out with Wuxi CEC PARK as a case study, and a comparative carbon emission analysis with assembled PC structure and cast-in-place steel-hybrid structure was carried out. The carbon emission calculation model comprehensively considers the six stages of the whole life cycle of the building, including the material preparation and component production stage, logistics transfer stage, construction stage, operation and maintenance stage, renovation and reuse stage, and dismantling and reuse stage, and covers the carbon emission activities of all elements of "human, machine and material", which guarantees the comprehensiveness and accuracy of the calculation results, and realizes the carbon emissions from steel structure components in the case of Wuxi CEC PARK. It also realizes the calculation of carbon emission factors of steel structure components. The results show that the average annual carbon emission intensity of the building is 58.53 kgCO2e?m-2?a-1, which is about 16.48 kgCO2e?m-2?a-1 less than that of the assembled PC structure and the cast-in-place steel-concrete structure respectively, 30.36 kgCO2e?m-2?a-1, showing the good carbon reduction effect of assembled steel structure buildings; the operation stage has the largest carbon emission, accounting for 58.33%; followed by the carbon emission in the material preparation and component production stage, accounting for 28.07%; in the building dismantling and reuse stage, the carbon emission is - 3840.29tCO2e in the dismantling and reuse phase, realizing the effect of carbon reduction in the recycling phase of the building; the carbon reduction value of renewable energy and plant carbon sinks of the building reaches -389.33tCO2e. The method proposed in this paper solves the problem of missing carbon emission calculation methods for the whole life cycle of assembled steel structure office buildings, provides a basis for the carbon reduction assessment of assembled steel structure office buildings, helps to popularize assembled steel structure as a structural form of building in the construction industry, and provides a reference for the research on the prediction of carbon emission of office buildings of the same type and the promotion of carbon reduction in the construction industry.