This study highlights a green approach for the reduction of graphene oxide (GO) using the ultraviolet/sulfite advanced reduction process (UV/sulfite process). X-ray photoelectron spectroscopy (XPS) provided a strong evidence on the efficient reduction of GO by increasing the C/O ratio from 2.0 to 4.8, and the successful reduction was also characterized by UV–Vis, XRD and Raman spectrometry. The reduction of GO was attributed to the hydrated electrons generated from both sulfite photolysis (major, contributed by 71.4%) and GO photolysis (minor, contributed by 21.6%) under UV irradiation. The dissolved oxygen in water exhibited inhibitory effect on GO reduction through scavenging of the hydrated electrons. Moreover, the reduction efficiency of GO decreased with the increasing UV wavelength from 254 nm to 365 nm, because of the reduced molar absorptivity of sulfite at higher UV wavelength. By using this green photo-reduction method, high-purity of reduced graphene oxide can be easily obtained by water-rinse, since soluble sulfite are the only by-products. In conclusion, the research outcomes provide mechanistic insights on the GO reduction by the hydrated electron-based advanced reduction processes, which has great potential for the environmental-friendly and cost-effective reduction of GO.