Abstract: With the large-scale development of subway construction, there are more and more cases of subway tunnel construction underneath passing existing subway lines. In order to ensure the safe operation of the subway, it is necessary to strictly control the construction of the subway line. The paper takes the application of cantilever tunneling machine construction method in short-distance underneath passing existing KUANGSHANFA subway tunnel as an example, analyzes the construction key points and safety measures of the cantilever tunneling machine cantilever tunneling machine, and summarizes the advantages and disadvantages of the selection of the cantilever tunneling machine. The project is the first successful application of cantilever tunneling machine construction method in Shenzhen existing subway lines, it is of great reference significance and can provide a reference for the subsequent construction of similar projects.