A calculation model for carbon emissions from the physicochemical stage was built to establish an integrated carbon emission factor bank based on quotas. The objective function is the lowest carbon emission from the physicochemical stage of the fabricated shear wall structure, and the variables are the section size of the beam, wall thickness, wall length, and strength of the concrete wall. Considering the strength, building condition, and displacement constraint of the member, an optimization model is established using the optimization software Lingo, and the optimal size of the member and the strength of the concrete are determined. The feasibility of the optimization method is verified using a practical case study, which provides a reference for further promoting the development of prefabricated buildings in the design stage.