Abstarct: The design and construction of underground structures in most cases are carried out with approximate knowledge of geomechanical parameters of the surrounding environments. Due to the difficulty of estimating the parameters of the earth, the behavior measurement and the application of the back analysis is a useful method. Monitoring during and after the project implementation is used not only to control the stability of structures but also to re-estimate the input data for geomechanical parameters. In the design analysis, this estimate should be made in such a way that the distance between actual and predicted values for the environment examination is minimized. The main purpose of the monitoring is to determine the stability conditions in an underground structure by providing quantitative information baxsed on land monitoring and tunnel maintenance system. In the back analysis, it is not merely the determination of the mechanical model, mechanical constant values and its external forces, but the ultimate purpose is to assess the design method during construction. In this study geomechanical parameters of soil are replaced by a single-variable and baxsed on instrumentation data for tunnel line 2 of Mashhad Metro. Laboratory data is used as equivalent geomechanical parameters in modeling with FLAC 3D software. After the back analysis, the values of the deformation modulus (Em) and the horizontal to vertical tension ratio (K) were calculated to be 199 mega-Pascal and 0.48 respectively. By correcting the initial values of geomechanical parameters, the stability analysis of tunnel line 2 of Mashhad Metro in the studied section was carried out using method (DSCT) and it was determined that the tunnel will be stable considering the maintenance.