Abstract: The interfacial bonding performance between the liner and composite material (CFRP) in vehicle-mounted high-pressure type IV hydrogen storage cylinders is a key factor to ensure the safety of the cylinders, and it is particularly important to carry out the research on the interfacial behavior between the liner and the composite material. In this paper, the surface of polyamide 6 (PA6) was modified by plasma surface treatment process to enhance its bonding strength with CFRP, and the bonding performance of CFRP-PA6 under different surface free energies was systematically studied on this basis. The effects of plasma treatment on the surface morphology of PA6 and the CFRP-PA6 bonding interface were observed using 3D laser measurement microscopy and high-resolution field emission scanning electron microscopy (SEM). Further, based on the microscopic observation results, a CFRP-PA6 microscopic finite element model was established to compare the experimental data and deeply analyze the change mechanism of the interfacial bonding performance. The results show that the plasma treatment significantly increases the surface free energy of PA6, which enhances the bond strength from 0.35 MPa to 12.38 MPa, an increase of 31 times. However, when the surface roughness exceeded a certain threshold, the bond strength decreased due to the formation of tiny craters and liquid surface tension. In this study, the debonding phenomenon at the CFRP-PA6 interface was successfully simulated by introducing the concept of rough surface to the microscopic model, which provides theoretical basis and technical support for the design and manufacture of high-pressure IV hydrogen storage cylinders for vehicles.