An “aluminum/graphene oxide/aluminum (Al/GO/Al)” interface model with different carbon/oxygen ratio or with different defects was established. Effects of oxygen-containing functional groups and different defects on the interface of reduced graphene oxide/aluminum composites was studied using first principle method based on density functional theory (DFT). The results show that the epoxy group is better than carbon atom to produce obvious charge interaction with aluminum atom in the interface model of Al/GO/Al. The net charge of oxygen atom is -0.98 e while aluminum atom is 0.46 e, which is conducive to the interfacial bonding between reduced graphene oxide (RGO) and aluminum matrix in composites. When the defects exists, the net charge of carbon atoms at the defects in the Al/GO/Al interface model is in the range of -0.05 e to -0.38 e. Interaction between epoxy group and carbon atoms is weak, while interaction between epoxy group and aluminum atoms is significantly intensified. The existence of epoxy group can inhibit reaction between carbon atom and aluminum atom in the vacancy defects, and protect integrity of carbon structure in RGO with vacancy defects. Therefore, this research may provide theoretical guidance for development of high-performance Al/GO/Al matrix composites.