Abstract: In order to study the effect of different carbon nano，aluminum content and different heat treatment processes on the mechanical properties and microstructure of Mg-based composites，carbon nanotubes reinforced matrix composites CNTs/AZ91 were prepared by stirring casting method.The mechanical properties of the T4 state and the T6 state were investigated，and the micro structure of the material was observed and analyzed.It was found that the strength of the material after the addition of carbon nanotubes was improved，but the plasticity was decreased，and the carbon nanotubes microstructure of composite materials.When the aluminum content increases，the elastic modulus of the composites is improved，and the reasonable heat treatment makes the mechanical properties of the composites improved，providing a reference for production and scientific research.