In this study, the prefabricated stress method is applied to the diamond polishing process to improve the success rate of large-size diamond polishing. Based on the difference in thermal expansion coefficients between the diamond film and the metal substrate, compressive stress is introduced into the diamond film by high-temperature bonding and cooling process before polishing to offset the tensile stress caused by friction heating up during the polishing process, so as to inhibit the generation and extension of cracks. The work aims to explore and verify the effectiveness of the prefabricated stress method in polishing large-size diamond film, to improve the success rate of large-size diamond polishing, and to provide a new technical way for improving the surface quality and application performance of diamond films.In this study, finite element analysis and experimental methods were used to verify the validity of the prefabricated stress method. The diamond film samples were tested by Raman spectroscopy and phase analysis of X-ray diffraction (XRD), and the Raman test data were used to introduce the residual stress in the diamond film in the finite element analysis. The typical fracture morphology of the sample cracking was observed by scanning electron microscope (SEM) through the polishing of bonded samples at room temperature. Combined with the finite element simulation of the diamond film stress change during the polishing process, it revealed that the stress caused by the friction heating up during the polishing process led to the cracking of the diamond film. Subsequently, finite element analysis was used to simulate the introduction process of prefabricated stress in the diamond film and its offsetting effect on the tensile stress during the polishing process, and the effects of bonding temperature and fixture thickness on the prefabricated stress were investigated. The results of finite element analysis show that under the same fixture thickness, the prefabricated stress increases approximately linearly with the bonding temperature. Under the same bonding temperature, the prefabricated stress increases rapidly with the temperature firstly, and then increases slowly after the fixture thickness reaches 30 mm, and gradually tends to be stabilized. The introduction of compressive stress into the diamond film through high temperature sample bonding can effectively offset the tensile stress due to the temperature rise caused by friction in the polishing process. The experimental results show that the diamond film with a diameter of 125 mm has been successfully polished by the prefabricated stress method under the conditions of fixture thickness of 50 mm and sample bonding at 90 ℃. Through a combination of finite element analysis and experimental verification, the proposed prefabricated method significantly improves the polishing success rate of large-size diamond films, demonstrating its effectiveness and feasibility. The results show that by utilizing the difference in thermal expansion coefficients between the metal fixture and the diamond film, the compressive stress introduced during the high-temperature bonding and cooling process can offset the tensile stress generated by frictional heating up during the polishing process, thus inhibiting the crack formation in the diamond film. Future studies can further optimize the prefabricated stress introduction conditions to further improve the polishing quality of diamond films.