Abstract: Factors such as construction, train operation, foundation settlement, and passenger boarding can cause deformation of railway passenger platforms (referred to as platform), invade the space of train operation and cause train accidents. Therefore, it is necessary to regularly measure the size of the platform outline to ensure the safe operation of trains. This paper elaborated on the measurement method and accuracy requirements for platform limit, and proposed a platform limit measurement method based on 3D laser scanning. It utilized high-precision laser radar and other equipment mounted on the track detection car to collect platform three-dimensional point cloud data and perform fine processing of the point cloud data. Combined mileage data to restore three-dimensional space, the paper established an accurate platform structure model, and implemented the measurement of the horizontal and vertical dimensions of the platform limit. The results of the platform test at Beijing West Railway Station show that the measurement accuracy of this method can meet the requirements of the specifications and has practical engineering application value.