Abstract: The Al-12Si-3Fe-3Mn-2Ni alloy powder has been sprayed on the surface of magnesium alloy with cold spraying technology.The interface morphology between substrate alloy and coating has been investigated.The effect of heat treatment temperature and holding time on the diffusion behavior between coating and substrate alloy has been studied.The results show that the Al-12Si-3Fe-3Mn-2Ni alloy powder coating by cold spraying technology becomes more density and homogeneous after heat treatment.Al in the coating diffuses into the substrate alloy and Mg in the substrate alloy diffuses into the coating.Moreover, the diffusion amount diffused into the coating from the substrate alloy is more than that diffused into the substrate alloy from the coating.With an increase of temperature and holding time, the diffusion degree of Al and Mg between the coating and substrate alloy get sufficient.However, the diffusion layer varies little when the temperature rises to 300℃ and the holding time increases to 3 h.Little diffusion of other alloying elements in the coating and substrate alloy has been observed.