Fracture often occurs in the metal layer of the COF (Chip on Film) transition zone when OLED(Organic Light-Emitting Diode) screens are at the module-bending stage and the reliability verification stage. Based on the design of experiment (DOE), this paper uses a L₉(3⁴) orthogonal test scheme to optimize four influence factors: the thickness of the foam, the offset of the foam, the thickness of the MCL(Metal Cover Layer), and the offset of the U-film. Two indexes, the metal layer stress in module-bending stage and the reliability state, respectively are employed and optimized to be minimal. In the L₉(3⁴) orthogonal DOE test scheme, finite element method are used to analyze nine groups of COF zones with different influence-factor combinations, and experimental tests are also carried out for verification. The results show that the U-film attachment offset has the greatest influence on the bending stress of the COF metal layer, while the foam thickness has a weaker influence, and the MCL thickness and foam attachment offset have the least influence. For the optimal influence-factor combination, both the module-bending stage and the reliability state have the least metal layer stress, with values of 57 MPa and 523 MPa, respectively. Compared with other combinations, the optimal influence-factor combination have 100% of the yield rate during the experimental tests,satisfying design and production requirements.