In this study, using the collected data from 4 slope failures in one of the central mines of Iran, the shear strength parameters of jointed and crushed rock masses using back analysis method are calculated and its results are compared with the values obtained from the empirical methods. In this regard, firstly, the identification of failures is investigated and then geometrical and geological engineering parameters of slopes are collected and recorded by field survey. At this stage, using the Hoek-Brown criterion, shear strength parameters of the rock mass are estimated. Then, using appropriate software for slope stability analysis (limit equilibrium method software: SLIDE and numerical method software: FLAC), and assuming that safety factor is one, the shear strength parameters for sliding surfaces are determined. Finally, the results obtained from this analysis are compared with the results of the empirical methods and then suggestions are made to modify the input data of empirical method