Abstract: In the design process of railway project, it needs to strictly control the difference of altitude between two parallel lines. The traditional method based on CAD will require designers to keep inspecting the altitude in base section of two lines for the calculation of difference, which will cause heavy workload and low accuracies.For addressing this problem, this paper is combing Rhino, which is a BIM design software, with the visual programming plugin Grasshopper to design a method to inspecting the altitude difference between two lines, and the reliability of the method are being verified. This method is being used in the JinAo Temple segment of Line 18 in Chongqing Metro, and the proposed solution has achieved the same results compare with the traditional methods, which has validated the effectiveness of the new method. Meanwhile, it also shows that the data analysis and process by using BIM technology can help to improve the efficiencies of railway project, which can lead to the adoption of parametric and lean design.