This paper presents a detailed study of gap-filling method to fabricate graphene films with high quality on polished Cu substrate. The nucleation density of graphene domains (GDs) reduces on the electrochemically and mechanically polished (ECMP) Cu substrate. Through the optical microscope and scanning electron microscope (SEM) testing of the graphene domains grown on the unpolished and polished Cu substrate, it demonstrated that the surface morphology of the Cu substrate was crucial in reducing the nucleation density and increasing the size of GDs. The Raman maps demonstrate that the GDs were homogeneous and monolayer graphene domains. Then large-area homogeneous monolayer graphene films with large-scale hexagonal domains were synthesized on the polishing Cu substrate by the gap-filling method. The process of preparing high quality graphene film by gap-filling method is explained through flow chart. Consequently, the technique of fabricate graphene films with high quality on polished Cu substrate by gap-filling method proposed in this paper can conveniently improve the properties of graphene films and graphene-based photoelectronic devices.