Interfacial reactions and growth kinetics between molten Mg-40Al and solid Mg-20Ce were investigated. Reaction temperatures were at 475°C, 500°C and 525°C, with reaction time ranging from 5min to 30min. Al₁₁Ce₃, Al₃Ce and Al₂Ce were formed via the reaction of Al and Ce in the diffusion reaction layers. The volume fraction of the intermetallic compounds in the diffusion layer increased with temperature. The growth kinetics of the diffusion reaction layers was well conformed to the parabolic law. The activation energy for the growth of the diffusion reaction layers was 42±3.7kJ/mol. Liquid-solid diffusion experiment can better understand the formation of compounds in the smelting process. Kinetics datum were provided for the formation of the compound during the smelting process.