Abstract: Surface treatment can effectively enhance the interfacial bonding performance between AZ31B magnesium alloy and CF-PEEK. In this study, two common surface treatment methods(anodic oxidation and annealing treatment) were employed to prepare a granular anodic oxidation layer and a dense annealing-induced oxidation layer on the AZ31B surface,which formed a significant contrast with the smooth untreated surface. The effects of different oxide layers on the interfacial structure and mechanical properties of joints fabricated by ultrasonic-assisted hot-press welding were systematically investigated. The results indicate that both types of oxide layers significantly increase the surface energy of AZ31B, thereby improving interfacial compatibility and bonding strength, and markedly enhancing the mechanical performance of the joints. In particular, a newly formed MgCO₃ chemical bond is identified at the interface between the anodic oxidation layer and CF-PEEK, further strengthening the interfacial interaction. The shear strengths of the joints subjecte to annealing treatment and anodic oxidation reache 15.3 MPa and 47.9 MPa, respectively, representing increases of 139% and 648% compared to the untreated joint(6.4 MPa). The anodic oxidation treatment achieve effective strengthening of the AZ31B/CF-PEEK interface connection through both mechanical interlocking and chemical bonding.