To conduct a more in-depth study on carbon emissions and influencing factors during the materialization stage of prefabricated buildings, this paper focused on a residential prefabricated building in Beijing. The LCA method, combined with BIM technology, was utilized to establish a process-based “LCA-BIM” carbon emission statistical platform and to propose a carbon emission calculation method. The carbon emissions during the materialization stage were calculated. The results revealed that the production of building materials contributed the highest proportion of carbon emissions, accounting for 85.73% of the total emissions during the materialization stage. Specifically, reinforcing steel and concrete dominated the overall carbon emissions from building materials, accounting for 97.44% of the total. Through a quantitative analysis in the process of carbon emissions calculation, the main factors influencing the carbon emissions during the production stage of building materials were identified. This study adopts a combined approach of empirical analysis and a literature review, establishing six basic hypotheses for four aspects: material selection, energy consumption, material storage, and carbon emissions in the production stage of building materials. A structural equation model was used to theoretically validate the influencing factors in the production stage of prefabricated building materials. SPSS27.0 and AMOS28 software were employed for data analysis. From the perspective of the overall impact, material selection had the strongest overall impact on the production stage of building materials, followed by energy consumption, while material storage had the smallest overall impact. From the perspective of direct impacts, energy consumption had the strongest direct impact on the carbon emissions in the production stage of the building materials. The findings of this study can provide a theoretical reference for national institutions and businesses for carbon emission evaluation and decision-making.