The second stage beginning to materials institute of Beijing metro line 6 line station shield receives well cross-channel excavation span of 15.6m, using double side heading method construction and secondary lining construction of temporary wall support in dismantling, the security risk is very large. This project uses to keep some temporary I-strut, to effective water repellent treatment on the basis of secondary lining construction of tunnel deformation and the impact on the surrounding environment has been reduced, ensuring pipeline safety above the tunnel, and achieved good results, but also provides a set of applicable metro excavation under complex environment construction technique of second lining of tunnel with large cross section.