A three-dimension finite element model (FEM) was used to analyze the effect of particles with different shapes, volume fractions and particle sizes on the mechanical properties of SiC particle reinforced aluminum-matrix composites. The results show that the particle shape has greater effect on the stress of particle, the strain of matrix and the ductility of composites than that of the particle size and volume fraction. There are serious stress concentration round the particle corner and strain concentration in the matrix adjacent to the particle corners along the load. The stress increases quickly, the ductility decreases and the elastic modulus increases with decreasing the particle corner degree. The stress decreases and the elastic modulus increases with increasing the volume fraction of SiC particles. The particle size has little effect on the stress and strain of the composites with small particle size