In this study, a comprehensive examination of deformation of Al particles impacting on Al substrate was conducted by using the Arbitrary Lagrangian Eulerian (ALE) method to clarify the deposition characteristics of Al powder and effect of surface oxide films in cold spraying. It was found that the deformation behaviour of Al particles is different from that of Cu particles under the same impact conditions owing to its lower density and thus less kinetic energy upon impact. The results indicate that the Al particles need a higher velocity to reach the same compression ratio as that of Cu particles. On the other hand, the numerical results show that the oxide films at particle surfaces influences the bonding condition between the particles and substrate. The inclusions of the crushed oxide films at the interfaces between the depostied particles inhibit the deformation.