Abstract: Taking Galongla tunnel as an example, a finite element model of variable parameters is established according to the geological conditions. On the basis of deformation monitoring data, back analysis is performed for the mechanical parameters including elastic modulus, Poisson's ratio, cohesion, internal friction angle and lateral pressure coefficient in order to get the real values of surrounding rock. Then the proposed sensitivity analysis method is employed to study the sensitivity of the mechanical parameters of surrounding rock to deformation. The results show that, for vault settlement, the elastic modulus is more sensitive than the other parameters. For the surrounding convergence which is opposite to the vault settlement, the Poisson's ratio, cohesion and internal friction angle are more sensitive than the elastic modulus. The results of this study have a certain reference value for the stability analysis of Galongla tunnel.