A trajectory measurement of combination vehicles is proposed based on machine vision, which can be used to calculate steering characteristics parameters. Firstly, the land marks composed of several horizontal and vertical identification lines are designed and pasted in experimental field. Secondly, the cameras installed on the vehicle capture the driving video streams, and the intersection coordinate can be calculated by the threshold segmentation and the curve fitting of the horizontal and vertical identification lines. Finally, the global coordinates of the cameras can be calculated by the geometrical deduction, and then the trajectory of the point on the vehicle can be calculated. At the end of the paper, we compare our method with GPS trajectory measurement. The experimental results suggest that the trajectory measurement based on machine vision possesses the advantages of high speed, high precision and high validity and provides a new solution for the measurement of curve possibility for combination vehicles.