The three-dimensional finite element simulating and its results of the horizontal and verti-cal displacement of the top, the side, the underside of metro and downlink tunnels were carried out bythe ABAQUS finite element simulation analysis software .The results show that there are obviouseffects of foundation pit excavation on underground existing tunnels and the vertical displacement ofthe tunnel locating in the central position of the foundation pit and the horizontal displacement of thetunnel locating in the edge position of the foundation pit are relatively large.What's more, the verticaldisplacement of the top is larger than the side and the underside of the same tunnel and the horizontaldisplacement of the side are larger than the top and the underside of the same tunnel.In the effect ofexcavation unloading, the deformation of tunnel performance that the vertical diameter increases andthe horizontal diameter decreases.We should pay more attention to the foundation pit excavation loca-ting above the existing tunnel.