Abstract: Aiming at the problems of long design cycle, the inability of real-time dynamic display of design effects and the non-cross-platform linkage of design products in the design process of rail vehicles, a virtual design system for rail vehicles based on Unity3D virtual engine is proposed. Based on this virtual design system, the whole process of virtual design from the overall design, key component structure design, virtual disassembly and assembly to virtual running test is developed and realized. Realize high-efficiency and high-precision human-computer interaction by using fan-shaped collision inspection and AABB enclosing detection method based on mountain climbing method; applying model instantiation technology to reduce the amount of system models and achieving lightweight design; applying Ansys dynamic link to realize Unity3D and Ansys Platform linkage. The results show that the system realizes the low-cost, high-efficiency, multi-style design process of rail vehicles, and provides a reference direction for the design and application of virtual reality technology.