Back analysis of strength parameters utilize for inputs parameter in order to stability analysis, optimal support system design, safety support system and modeling mechanized excavation by TBM and determining surface subsidence of adjacent buildings in the urban area. Also, due to the complexity of geological structure, a large number of field tests are needed to determine these parameters and these tests are expensive and time-consuming. So, back analysis do not need more time and expenses and present acceptable method for determining strength parameters of rock mass and soil. In this study, back analysis of strength parameters during the path based on instrument has been evaluated. influence of each parameter was examined with Sensitivity analysis . in back analysis of line A in Ghom metro , genetic algorithm and direct univariate algorithm were used for strength parameters and acceptable error was obtained. Unknown parameters in back analysis are elasticity module, coefficient of in-situ stresses, internal friction angle and cohesion. The optimal values of these 4 parameters using back-analysis are 25 MPa, 0.8, 30 degree and 20 kPa respectively.