Herein, a sensitive photo-electrochemical sensor based on C3N4 and reduced graphene oxide nanosheets modified glassy carbon electrode (C3N4-RGO/GCE) has been fabricated for the detection of rutin under UV light illumination. In C3N4-RGO catalyst, RGO not only works as a template but also promotes electron transfer, meanwhile, C3N4 acts as a photocatalyst. Benefiting from the superior electron transfer capacity and efficient UV light effect of the C3N4-RGO catalyst, we get a photo-electrochemical sensor for the rutin detecting with a low detection limit of 1.78×10−9molL−1 and an excellent linear range of 5×10−9–1.4×10−4molL−1. Meanwhile, the achieved C3N4-RGO/GCE demonstrated nice selectivity, good reproducibility as well as reliable stability. Moreover, compared with the electrochemical determination, the C3N4-RGO electrode provides a new way for rutin detection by photo-electrochemical method with a promising UV light responsive result.