High-temperature graphitization of graphene oxide (GO) is a crucial step for enhancing interlayer stacking and repairing the in-plane defects of reduced graphene oxide (rGO) films. However, the fine control of the structural repair and reducing the energy consumption in thermal treatment remain challenges. In this study, ab-initio molecular dynamics simulations combined with experiments are used to investigate the structural evolution of rGO upon thermal annealing, with or without the presence of single-layer graphene (SLG). It is found that the SLG promotes the repair of the carbon honeycombed matrix and alleviates the release of carbon-containing groups during graphitization. Further electronic analysis reveals the crucial role of charge transfer from SLG to defective graphene in strengthening the C─C bonds. The result of Raman spectroscopy matches with the simulation, demonstrating an improved repairing degree of rGO upon contacting with SLG. This study provides a deeper understanding of the graphitization and repair mechanism of rGO, which may be useful for the highly efficient preparation of high-quality graphene films.