In order to accurately determine the mechanical parameters of jointed rock mass in Lirang tunnel, the discrete fissure network (DFN) technology in the 3DEC program is used to establish a discrete fissure network model which can reflect the characteristics of the joint fracture distribution. On this basis, combined with the laboratory rock and joint mechanics test, the equivalent rock mass model based on the DFN-DEM coupling method is established by using the equivalent rock mass technology and 3DEC program, and a multi scale equivalent jointed rock mass calculation model reflecting the characteristics of the jointed rock mass distribution is constructed. Then by means of uniaxial compression test on the calculation model of multi-scale equivalent jointed rock mass, the mechanical properties of rock mass before and after peak are obtained, and the size effect, anisotropy, characterization unit and equivalent rock mass mechanical parameters of jointed rock mass are analyzed. The results show that the DFN-DEM coupling technology solves the modeling problem of non penetrating joints. With the increase of the equivalent rock mass scale, the peak strength and elastic modulus of jointed rock gradually decrease, and the anisotropy gradually decreases, and the scale reaches 5×5×10m to stabilize the characterization unit; The mechanical parameters of equivalent rock mass at the unit body scale are as follows: The modulus of elasticity is 9GPa, the uniaxial compression strength is 0.7MPa, the internal friction angle is 25 degrees, the cohesive force is 0.3Mpa, the tensile strength is 0.12Mpa. Compared with the mechanical parameters obtained by the Hoek-Brown strength criterion, the two are relatively close.This method provides a basis for further research on stability of engineering rock mass.