In this study, AuM (M = Pt, Pd) bimetallic hexagonals (AuM BHGs) were successfully combined with graphene quantum dots (GQDs) by a simple method at ambient temperature (~ 30 °C) to form AuM BHGs/ GQDs nanocomposites with enhanced properties and electro‑activities. The synthesized AuM BHGs/ GQDs were also characterized by UV–Vis, XRD, FTIR, XPS, AFM, TEM, and EDS. The novel AuM BHGs/GQDs were successfully synthesized, possessed an average particle size of AuM BHGs (~ 50–60 nm) and GQDs (~ 6–16 nm), and were homogeneously distributed in the dispersion. Furthermore, AuM BHGs/GQDs nanocomposites were also investigated as a sensitive sensor in the H2O2 detection by cyclic voltammetry method, with a low H2O2 limit of detection (LOD) of 0.865 nM, high sensitivity of 1.27 μAnM−1cm−2 and a wide detection range from 10–12 to 10–3 M. Therefore, AuM BHG/GQDs nanocomposites could be used to detect H2O2 with high sensitivity and fast response.