Abstract: Currently on the detection of heat exchanger tube and pipe reactor, film imaging is the main method, which not only requires constant input costs but also reduces detection speed. So a new system is developed, which uses stepper motor to drive the linear array detector rotating around the axis and scanning the weld. The data would be transmitted to the computer and the key data would be picked up to build the circular scanning image. After being gray processed, the image would be shown to the users on the computer screen. Besides this, the system has the following practical functions: assistant judgment on defects, measuring the size of the defect, pseudo-color processing, median filtering, rotating image, scaling image, moving image and so on.