The urban karst geology is easy to cause the shield machine to fall and fault, and the cavern collapses. The problem of the influence of the karst cave on the tunnel in front of the shield tunneling depends on the Dalian Metro Line 5, based on theoretical analysis and MIDAS GTS numerical simulation test, with surface subsidence, deformation of the tunnel and plastic zone as the analysis index, the size of the cave and the filling of the cave were selected as the analysis conditions, and the distance from the tunneling to the cave was taken as a variable, contrast analysis after pretreatment with karst caves and before treatment. The results show that different cave sizes and different fillers have little effect on the top of the cave roof and the vertical deformation of the surface. When the tunneling is close to the cavern, the horizontal deformation of the tunnel waist and the longitudinal deformation of the temporary plane near the heading surface show a nonlinear growth. It is related to the size of the cave; the plastic zone penetration distance between the tunnel face and the cave is linear with the size of the cave. The theoretical calculation results are consistent with the numerical simulation results. The deformation of the cave after treatment is effectively controlled, and the numerical simulation results are close to the measured data. The research results provide reference for karst identification treatment and construction.