Abstract: The influence of particle size on the dynamic behavior of particle-reinforced metal-matrix composites was investigated through the finite element method under different strain rates. The three-dimensional cubic unit cell models which contained one or several SiC particles were employed. The diameters of the particles were 16 μ m and 7.5 μ m, separately. And the arrangement of the multi-particles inside the unit cell mode was random. The stress-strain behavior of the matrix material is assumed to be power-law strain hardening and coupled with power-law strain rate hardening. The simulation results show that the influence of particle size on the dynamic behavior of PMMCs is coupled with the volume fraction of the particle and the strain rate. The smaller the diameter of the particle, the better the reinforced effect, when the volume fraction of the particles is constant. The flow stress increases with the increasing of the particle volume fraction and strain rates.