When traditional gauss projection method is used to treat long-span lines in east-west direction, the frequent change belt can solve neither the reference ellipsoid projection to Gauss plane projection length deformation nor the influence of the height to the length of the deformation caused by the domestication. Therefore, some scholars have proposed a new method to establish an ellipsoid of engineering based on the theory of least squares, rotation of space coordinate system and ellipsoid transformation. Based on this theory, the authors verify and analyze the method through the specific examples of high-speed railway GPS control network. The experimental analysis shows that this method can greatly reduce the deformation component of the transverse axial direction after the projection, avoid the phenomenon of Gaussian projection zoning, and effectively reduce the projection distortion caused by elevation. It is especially suitable for long line engineering with long span, and the mathematical model is mature and the calculation process is clear, which can be used for reference in line engineering measurement.