Abstract: In view of the limitations of traditional mesh-based numerical methods in simulating large deformation problems of geotechnical materials, this paper applies a meshless numerical method, smooth particle hydrodynamics (SPH), to simulate the whole process of shield tunnel excavation instability, including the progressive instability to the ultimate equilibrium state and then to the collapse large deformation after soil damage. The simulation includes the progressive destabilization of the soil body to the limit equilibrium state, and then to the collapse and large deformation of the soil body after destruction. First, the SPH model of shield tunnel excavation is established, and the feasibility of the SPH method in analyzing the large deformation problem of tunnel excavation instability is verified by comparing the SPH simulation results with the theoretical solution and the ultimate supporting force and excavation surface damage mode obtained from the model test. Then, under the condition of no supporting force, the effects of three key parameters, namely, cover-to-span ratio, angle of internal friction and cohesion, on the large deformation of the soil body collapsing after damage were analyzed. The results of the study provide a new analytical method and perspective for solving the large deformation problems of tunnels in the future.