Abstract: The effects of the reinforcing particle size and strain rate on deformation localization behavior of SiC_P/6151Al composites are investigated by making use of Split Hopkinson Bar and MTS-810 Materials Testing System with specially-designed hat-shaped specimens, which can produce a shear loading in the specimen. The experimental results demonstrate that the strengthening effect for the small-size particle-reinforced composite is higher than that for the large-size particle-reinforced composite. However, the small-size particle-reinforced composite is more prone to deformation localization than the large-particle composite under impact loading. The mechanisms leading to deformation localization in particle reinforced metal matrix composites are discussed in this paper as well.