The hybrid of a metal with graphene can improve electrochemical properties, but present hybrids cannot break through the limitations of their inherent properties because metals and graphene are conductors. This study reports the synthesis of a ruthenium-graphene quantum dot hybrid via the reduction of RuCl₃ with aspartic acid and arginine-functionalized graphene quantum dots (Asp–Arg–GQDs). Asp–Arg–GQDs act as the reducing agent, stabilizer, linker and semiconductor for the synthesis. The resulting Ru–Asp–Arg–GQDs possess a three-dimensional network structure composed of small Ru nanoparticles and small graphene sheets. The hybridization of Ru with Asp–Arg–GQDs results in the formation of a Schottky heterojunction at the interface. This unique structure improves the catalytic activity of Ru nanoparticles. The sensor based on Ru–Asp–Arg–GQD exhibits better sensitivity towards the electrochemical detection of carbendazim compared with the reported sensors. Differential pulse voltametric peak current increases linearly with an increase in the carbendazim concentration in the range from 0.01 μM to 45 μM with a detection limit of 0.004 μM. The proposed method has been successfully applied in the electrochemical detection of carbendazim in strawberry. This study also provides a way for the construction of a metal–graphene hybrid with excellent catalytic performance in the fields of sensing, energy storage and catalysis.