In cutting and welding processes of the H-shaped steel whose section size is about 300(W) mm×300(H) mm, 400(W) mm×300(H) mm or larger, a vision inspection method is adopted and set up in work field actually. By CCD image processing and programming, this system can measure geometry size and deformation of the steel with the resolution of 0.2 mm, and provide coordinate parameters for orientation and position of cutting/welding torch. For the problem that needs 0.7‰ resolution and large depth of field to measure the large section size of H-shaped steel, a vision imaging system is presented. From the actual measurement results, it can be seen that this system has a good measurement repeatability and stability. The theoretical analysis and experimental results show that the system achieves a resolution of 0.2 mm, and its processing time, from image capturing to final data uploading, meets the engineering requirements.