Abstract: The selection of mechanical parameters of rock mass based on numerical test is studied.The joint distribution model of rock mass is obtained through the field investigation and statistical analysis.The numerical model of rock mass characterization element based on the statistical analysis is constructed by using 3D random joint simulation technology, and the uniaxial compression numerical tests are carried out to determine the REV.Triaxial compressive tests are carried out to determine the shear strength parameters of the rock mass.Research results show that the REV size is 2 m×2 m×2 m, and mechanical parameters of rock mass and based on Heok-Brown intensity index is relatively consistent; the block using the Morh-Coulomb sliding constitutive model and the joint using Coulomb constitutive model can well reflect the study of mechanical properties of the breccia body; the selection method for mechanical parameters of rock mass based on the REV is reasonable.