Carbon emissions from the building sector account for around half of China's national CEs and have been the obstacle to reaching China's two-carbon goal. However, whether the prefabricated technique can mitigate CEs for the building sector is still argued by studies. In consideration of this, this study proposes an LCA and BIM-simulation integrated model to comprehensively calculate CEs of prefabricated (PBs) and traditional cast-in-situ buildings (TBs). The BIM simulation is verified by an analytical method. The results show that the total carbon emission intensity (CEI) of PB is 9.61 % lower than that of the TB, showing a significant advantage in CE reduction potential and can be chosen as the developing direction in the future. The main CEs come from the operation and maintenance stage, where the TB emits 11.02 % higher CEs than those of the PB. For the materialization stage, where CEs are centralized in a short period, the difference between CEIs of the PB and TB is 3.32 %, which is not significantly different. The collected data and calculated results in this study can be quite beneficial to future sustainability studies in the same research domain, especially the integrated application of BIM and LCA. This study also contributes to knowledge by proposing a comprehensive CE calculation model and providing reasonable measures for CE reduction, which is beneficial to the sustainable development of the building sector to achieve China's two-carbon goal.