Carbon nanomaterials (graphene and carbon nanotubes) possessing excellent mechanical properties, outstanding thermodynamic stability, and superior electrical conductivity, are regarded as the ideal reinforcement for metal matrix composites. The employment of carbon nanomaterials in the magnesium alloy composites help to overcome the low strength, hardness, and modulus of magnesium alloys. However, due to the paucity of chemical reactions between magnesium and carbon nanomaterials and their poor wettability, the interfacial strength between the two materials is weak, thereby limiting the performance of the reinforcement. The utilization of interfacial regulatory substances is a conventional approach to enhancing the bonding strength at the interface of composite materials. This paper mainly introduces the preparation methods and types of interfacial regulatory materials for carbon nanomaterials reinforced magnesium matrix composites; focuses on the methods of adding interfacial regulatory substances to the composites, the interfacial bonding of interfacial regulatory substances to reinforcement and matrix, and the mechanism of improving the interfacial bonding strength of the composite materials.