In order to improve the measurement accuracy of the large target intersection measurement system, the miss distance formula of target was derived by analyzing the principle of intersection measurement. According to the parameters of the formula, a mapping model between the pixel coordinate and the offset angle was established by using the geometric relationship. A calibration method for linear camera was designed by using grating scale according to the model. This method takes the whole optical system as a whole and does not need to consider the parameters of the camera, which directly calibrates the mapping relationship between the coordinates and their corresponding offset angles. The experimental results show that the average measurement error of the calibrated intersection measurement system at 1.4 m is 0.4 mm, and the maximum measurement error is better than 0.6 mm. The proposed method is simple but effective, and can improve the speed of the calibration and satisfy the accuracy requirement of the system.