A numerical model based on finite difference method(FDM) in FLAC3D is proposed to simulate the fracture of nonuniform rock materials. Weibull distribution is introduced to describe the distribution characteristics of elastic modulus and uniaxial compressive strength in each mesoscopic element which exhibits elastoplastic strain softening mechanical response. Then

this numerical model is used to investigate the effect of the mesoscopic nonuniformity and mesostructure on the macroscopic properties of numerical specimens under uniaxial compression. The results show that: (1) With the improvement of mesoscopic nonuniformity

the nonlinear characteristics of the numerical specimen gradually weaken and the brittleness gradually increases. Besides

the macroscopic peak strength and elastic modulus are linearly increased with ln(m) and 1/m respectively. Meanwhile

the failure mode of numerical specimens changes from plastic flow failure to shear failure and further to tensile failure. (2) When the mesoscopic nonuniformity indices keep constant

the mesostructure or mesoscopic elements space arrangement is the main factor that determines the fluctuation of rock mechanical behavior. Both the near-peak and post-peak phases of the stress-strain curve are sensitive to the spatial arrangement of the mesoscopic elements; but the pre-peak phase is opposite.