In order to provide accurate guidance for many deviation factors in tunneling and reduce the potential danger of manual measurement of shield tail clearance, an automatic measurement scheme for shield tail clearance for shield tunneling machine was proposed. The space structure of the tail clearance of the shield tunneling machine was analyzed, the shield tail clearance was marked by using laser and extracted by using industrial camera; the industrial networking communication and remote control were carried out based on TCP/IP; the automatic measurement of the shield tail clearance was realized by using the vision library of digital image processing technology OpenCV. A Qt-based PC client software was developed based on a shield tunneling machine with a diameter of 8 m.The experimental results show that the measurement method can meet the actual measurement requirements of the construction site.