Abstract: To solve the problems of large workload, low modeling accuracy, and weak applicability of existing 3D design software in complex structural forms of railway engineering, this paper established a component data storage standard. Based on the engineering assembly approach, the paper used a single component as a design unit for parameterized pre-design, implemented real-time interaction between parameters and models, abstracted spatial geometric lines as design parameters and defined them as linear constraints to constrain the position and shape of components, implemented refined design and assembly of components, stablished a mapping relationship between component attributes and the engineering quantity calculation template, imported component parameters into the template, and quickly calculated the engineering quantity, generated a 2D image by cutting the geometric contour lines of the components. This study reduces the difficulty of fine-grained design of complex individual components in railway engineering, and effectively improves the efficiency of modeling and modifying complex structures.