The process of shielding changes the additional stress of the above existing tunnel which causes the deformation of the tunnel and has certain influence on the structural safety of the existing tunnel. The Mindlin solution can be used to calculate the additional stress along the central axis of the existing tunnel caused by the shield driving parameters such as the compressing pressure of the cutter-head q, friction of the shield skin f, synchronous grouting pressure p. The additional stress caused by soil loss can be calculated by the image method theory. Winkler foundation model can be used to calculate the deformation of the existing tunnel. According to the different crossing processes, the total deformation of existing tunnel can be calculated by combining the above four parts of deformation. Finally, comparing the theoretical results with the measured data of metro construction project in Hangzhou, the valid of the method is confirmed.