In this paper, starting from pinhole imaging geometric model of the camera, according to the linear relationship of the image point and the object point, further analysis the scenery spot of on-board camera of the relationship between the image coordinates and the actual coordinates, found that cannot by establishing the mapping relationship between the image coordinates and the actual coordinates to measure the height of obstacles. So this paper presents a new calibration method, by interpolation method and least squares method to establish the mapping relationship between image height and actual height of the Scenery, namely the calibration model of on-board camera, to test the model, and the test result of maximum deviation is 0.07875cm, the minimum deviation is 0.01399cm, the average deviation is 0.03479cm, and the precision can be up to 0.11%. The method can accurately measure the height of obstacles, has a certain practicality and feasibility, suitable for the calibration of on-board camera, provide an effective reference for the research of automobile auxiliary driving system.