In this paper, the microstructure and microhardness of the Al-12Si coating produced by cold spraying with a relatively large powder were investigated. It is found that a thick, dense and well bonded Al-12Si coating could be produced by cold spraying with a relatively large powder through the control of spray conditions. The critical velocity for large Al-12Si particles was about 500 m/s under the spray conditions in this study. The as-deposited coating had the same phase as the Al- 12Si powder. The localized interface melting occurred resulting from both the adiabatic shearing upon impact and the thermal effect of hot gas. The precipitation of fine Si particles occurred in α-Al matrix in the coating deposited at an elevated gas temperature because of the thermal effect of hot gas during coating deposition. The dispersed Si particles in the coating improved the coating microhardness.