This book mainly focuses on two topics: • The early warning system of the metro structural safety, which includes the monitoring system and inspection system; • The treatment technology for the tunnel disease. In the discussion of the early warning system, several advanced sensing technologies were introduced, which could easily and rapidly detect the potential diseases of the tunnel lining structure. Meanwhile, in the discussion of the treatment technology for the structural problems, several reinforcement measures were introduced in details and corresponding application cases in East China were put out to verify the effects of the measures. From this book, practitioners in the maintenance and repair of metro structures could learn the deformation mechanisms and help address the practical issues they encounter.