Aiming at the problem that the telecentric lens cannot adjust the field of view due to its own characteristics, and it is difficult to adapt to the problem of obtaining the complete image of the part at one time when measuring the linear bearing, the HALCON image processing software is used to measure the length of the linear bearing through the image stitching method. Considering the effect of feature point extraction and edge contour acquisition, using the combination of backlight and forward lighting, a linear bearing measurement system based on combined lighting is established; in image stitching, a method of using images in the approximate overlap area of the image is proposed. The method of pyramid hierarchical search performs feature point detection and matching to improve the efficiency of image stitching; finally, the edge location of the image is performed by the Canny operator and the least square fitting method, and the length measurement is completed. The experimental results show that: the combined light source can better take into account the effect of image surface feature points and edge contour extraction; the detection time of the proposed stitching method is about 0.2S, which is 88% less than the traditional method; The visual measurement error based on image stitching is less than 0.1mm. In terms of measurement repeatability, it is more stable than traditional methods, and the maximum standard deviation of measurement is 0.005. Therefore, the detection efficiency, accuracy and stability of the vision system are guaranteed, and it has a certain theoretical basis and practical value in industrial automation detection.