Abstract: Combined with the damage mechanics method of fractured rock mass，and based on the Mohr-Coulomb theory model，the emergence and expansion of rock fractures are investigated in order to achieve the constitutive relations and evolution equations of partial rock destruction.Based on the two secondary development program interface of FLAC3D，VC++ programming language is used to realize the user-defined constitutive model which is compiled into a dynamic link file for loading and transferring.Finally，this constitutive model is applied to stability analysis for a roadway surrounding rock in the excavation，obtaining that the distribution rules of calculated plastic zone，displacement field，stress contours of distribution are accord with Mohr-Coulomb criterion，which validates the applicability and reliability of the model further.This provides a method for engineering application．

Key words: Fractured rock mass, Damage evolution, Surrounding rock of roadway, Constitutive model