Abstract: Rock materials are heterogeneous, and the strength of mineral particles and cementitious materials obey Weibull distribution statistically. Based on the combined finite-discrete element numerical method (FDEM), the parameter assignment process of elastic modulus and strength which obey to Weibull distribution is proposed. Then, the mechanical characteristics and failure behavior of heterogeneous rock samples under uniaxial compression, triaxial compression and Brazilian splitting are studied. Finally, the fracture and swelling deformation mechanism of heterogeneous rock mass around tunnel with high in-situ stress is investigated. The results show that: The FDEM numerical model, the number of triangular element with different elastic modulus obeys Weibull distribution, can be built by using the random parameter assignment method proposed in this paper; The uniaxial compressive strength, triaxial compressive strength, Brazilian splitting tensile strength, equivalent cohesion and equivalent internal friction angle of heterogeneous rock samples increase exponentially with the increase of heterogeneity m, and then approach to homogeneous materials; With the increase of m, the shape of fracture network changes little, mainly conjugate shear fracture, accompanied by a small number of tensile fractures, however, the failure degree of surrounding rock mass and the fracture propagation range decreases exponentially.