To simulate the mechanical properties of polymer bonded explosives(PBXs)from the meso-scale, the concept of gradation of Monte Carlo method was introduced into the PBX model of high volume fraction. A generating method of Voronoi polygon particles which can consider the distribution of graded particles was formed by combining the Voronoi polygon particle generation algorithm. A PBX meso structure model considering gradation and volume fraction of 94% and above was established through the treatment of particle modification, shrinking, corner cutting and smoothing etc. At the same time, the model can maintain periodic continuity at the boundary. The uniaxial compression simulation for PBX meso model of three groups under different gradation condition was performed by numerical manifold method(NMM). The equivalent elastic modulus obtained from NMM simulation was compared with the experimental results in literature. The reasons of deviation occurred between the simulation results and the experimental ones were analyzed, and the rationality of the PBX meso structure model generation method was discussed. Results show that the equivalent modulus of PBX increases with the increase of volume fraction, and the higher the volume fraction is, the faster the growth rate is. At the same time, when the volume fraction is below 30% and higher than 85%, the effect of the particle gradation on the equivalent modulus is smaller, but when 30%≤volume fraction≤85%, the effect of the particle gradation on the equivalent modulus is significant.