The metal-plastic combination is widely used in frontier fields such as energy storage technology and aerospace. This study proposes two metal surface treatment processes for metal-plastic composite injection molding. The first only involves the chemical treatment, whose interfacial bonding strength reaches 10.24 MPa. In the second, the plasma treatment is added to the chemical treatment process to increase the interface bonding strength to 17.58 MPa. The characterization result shows that the plastic is injected into the undercut microstructures to form a physical bolting force due to the countless microstructures after the metal surface treatment. Through the step-by-step study of the surface treatment process, it is found that hydrochloric acid solution causes a large-scale microstructure to appear on the metal surface, and the undercut nanostructure is obtained through the plasma treatment. This multilevel