The work aims to improve the antioxidation property of Al-Mg alloy powder and explore the application in energetic materials. Silane coupling agent (SCA) KH845-4 was chosen for surface modification of 30 μm atomized spherical Al-Mg alloy powder. Reaction temperature, reaction time, reaction concentration were chosen as the influence factors of the orthogonal experiment. The effect of surface modification was evaluated by thermal analysis test data. The oxygen content, morphology and particle size of Al-Mg alloy powder were analyzed by EDS, SEM and particle size analysis before and after the surface modification. After being treated by SCA, both onset temperature of the melting heat absorption and oxidative heat release of Al-Mg alloy powder increased, but the increasing range was limited. Antioxidation properties were affected by reaction temperature, reaction time and reaction concentration. The effect of reaction concentration on evaluation index of orthogonal experiment was the most significant and the effect of reaction temperature was the least. The silane film only isolated the contact between the active Al-Mg alloy powder and air. The crystal structure of Al-Mg alloy powder was not changed. SCA can effectively improve oxidation resistance of Al-Mg alloy powder. The best process scheme of surface modification is: reaction temperature at 40 ℃, reaction time at 1.5 hours and reaction concentration at 40%.