Energetic adhesives with excellent mechanical properties are of great significance for the development of solid propellant. In this paper, a small amount of graphene is used to enhance the mechanical properties of glycidyl azide polymer (GAP)-based energetic thermoplastic elastomer (GAP-ETPE), and an in-depth analysis of the graphene enhancement mechanism is conducted through the structural characterization of the composite elastomer. Scanning electron microscopy (SEM) reveals that the solvent-assisted ultrasonic dispersion method can fully disperse graphene in GAP-ETPE, taking advantage of its high specific surface area. Fourier Transform Infrared (FT-IR) and low-field Nuclear Magnetic Resonance (LF-NMR) analysis show that graphene can provide physical crosslinking sites, significantly increasing the crosslinking density of GAP-ETPE. Dynamic mechanical analysis (DMA) indicates that the increased crosslinking density caused by graphene will restrict the segmental motion of GAP-ETPE. Static tensile test result shows that the use of 0.1 wt% graphene can increase the tensile strength of GAP-ETPE from 7.0 to 7.8 MPa. This work provides a basis for the application of graphene in energetic adhesives.