The settlement control of the existing tunnel under shield tunneling is a key and high-risk problem in metro constructions. In order to explore the relationship between the construction settlement control methods and the settlement variation of existing structure in the process of underneath-pass excavation, the deformation of the existing structure of Shenzhen Metro Line 2 induced by underneath crossing of left-line of Gangxiabei Station-Lianhuacun Station on Shenzhen Metro Line No. 10 is monitored. A finite element calculation model is established based on the site monitoring data, and the relationship between the deformation of existing structure during shield crossing and the underneath crossing construction control method is obtained. The analytical results show that: (1) The synchronous grouting has a great influence on the initial deformation of the existing structure, and the secondary grouting has a great influence on the deformation stability time and size. ( 2) During the underpass process, it is necessary to pay attention to the maintenance of shield soil chamber pressure to maintain the chamber pressure at a higher level, and further to keep water and soil ahead of shield cutterhead. (3) The secondary grouting should be carried out in time after the segment comes out of shield tail, the hollows behind segment should be fully filled, and the secondary grouting should be carried out in time