Abstract: The pipeline internal diameter (ID) detection technology plays an important role in discovering pipeline hazards in advance and ensuring safe operation of pipelines. In this paper, a vision-based pipeline ID measurement and calculation method was developed by applying the Radon transform of vision measurement technology to the laser-source projection imaging method based on the machine vision technology. In this method, the laser transmitter is used to produce a ring which is completely in line with the internal shape of the pipeline. The image of the laser ring on the wall of the pipeline is collected by a camera and then transmitted to the computer for edge detection and refining treatment. And eventually, the cross section profile of the pipeline is obtained. What's more, two optical bands which reflect the information of pipeline ID are acquired by virtue of the Radon transform, and their center lines are extracted by means of refining treatment. And then, the pipeline ID data at all directional angles are calculated according to the distance between the center lines. It is indicated that this vision-based pipeline diameter measurement and calculation method is efficient and fast with high value of practical application, and it can obtain the information of pipeline ID at all directional angles at one time.