Abstract: Nuclear power steel structure engineering is characterized by stringent nuclear safety constraints, complex component types, intensive interdisciplinary coordination, and high requirements for quality assurance traceability. Traditional quantity takeoff based on two-dimensional drawings and experience-based design optimization can no longer support refined material management and control. Focusing on steel structure engineering for the nuclear island and conventional island main plant buildings, this paper proposes a material quantity precision calculation method based on a parametric BIM model as the data foundation, with component coding, attribute templates, quantity calculation rules, change closed-loop management, and quality traceability as the main line. Furthermore, it establishes a design optimization path integrating collaborative clash detection, section verification, joint standardization, nesting layout, and installation simulation. Practice shows that only by incorporating the quantity calculation model, fabrication model, procurement list, and on-site feedback into a unified data chain can statistical deviations in special-shaped plates, joint auxiliary materials, and variation quantities be reduced. This provides a reusable implementation method for procurement planning, cost control, construction organization, and quality assurance documentation archiving in nuclear power steel structure engineering.