Reduced graphene oxide (rGO) and Au nanodot (AuND, ∼1.5 nm) modified rGO, referred to as AuNDs-rGO, synthesized by a simple photochemical reduction method, are used for electrochemical biosensors. Our experimental results showed that the glucose oxidase (GOX)/rGO/Nafion/glassy carbon electrode (GCE) exhibits a linear range from 0.03 to 6.28 mM and a detection limit of 0.03 mM at a signal-to-noise (S/N) ratio of 3 for the amperometric sensing of glucose, while the GOX/AuNDs-rGO/Nafion/GCE shows a wider linear range from 0.02 to 8.82 mM and a lower detection limit of 0.02 mM. This difference may arise from the high catalytic activity of the AuNDs. Our studies demonstrate that the composites of rGO/Nafion and AuNDs-rGO/Nafion might offer a new class of electrode materials, and provide a promising platform for biosensing applications.