Abstract: The conversion from CAD drawings to BIM models is a common and urgent need for engineers, yet existing model conversion tools often result in missing information and require extensive modifications in the later stages. To address the need for rapid BIM structural model creation, this paper proposes a method to quickly establish BIM structural models from CAD drawings. First, the correspondence between CAD pixels and BIM structural model components is analyzed. Next, the key technologies for secondary development of CAD and domestic BIM software, along with the principles of automatic model conversion, are studied. Finally, a 3D model reconstruction system tailored to structural engineering is developed and applied to actual projects, demonstrating the feasibility of the method and the efficiency of the system.