Abstract: The existing ultimate displacement and its management reference are mainly determined after the closure of supporting structure of the common railway tunnel section, without considering the tunnel construction stages.Taking the existing high-speed railway tunnel which locates in surrounding rock of grade Ⅴ and adopts three bench method for example, it simulates the vault displacements in different construction stages by FLAC3D software, obtains the ultimate vault displacements in different construction stages based on cusp catastrophe theory. The results show that the ultimate vault displacements are affected by excavation of upper bench, middle bench, lower bench and invert in decending order and there is almost no effect by lower bench and invert excavation in the case of threebench construction in the surrounding rock of grade Ⅴ; under the calculated buried depth of 50-300 m, the ultimate displacement at vault in the same construction stage has a linear relationship with the buried depth. The sensitivities of surrounding rock parameters to the ultimate displacements are analyzed by grey correlation, and the influence degrees on the ultimate vault displacement are rock mass density ρ, elasticity modulus E, cohesive force c, poisson rate μ and internal friction angel φ in descending order.