Rutin acts to protect the cardiovascular system, and thus it is of great significance to detect rutin. CdSe quantum dots combined with poly(diallyldimethylammonium chloride)-modified reduced graphene oxide nanocomposites (CdSe QDs/PDDA-rGO) were synthesized and used to detect rutin. The linear detection range for rutin is 0.1 to 10.0 mu M and the detection limit is 0.03 mu M. Furthermore, the CdSe QDs/PDDA-rGO/ glassy carbon electrode (GCE) can quickly detect rutin in tablets. The new sensor is available to detect rutin in tablet samples.