The fabrication of a light-emitting device based on a composite consisting of cadmium sulfide nanoparticle, poly(vinylalcohol), and ruthenium 2,2'-bipyridyl complex is reported. The electroluminescence spectrum of this composite is similar to the combination of the emission from ruthenium complexes and cadmium sulfide. A stable electroluminescence at low threshold voltage (4 V), with a brightness of 680 cd/m2 and an external quantum efficiency of approximately 0.2% was achieved. it was demonstrated that the cadmium sulfide nanoparticles were able to improve the performance of the device and enhance the electron carrier mobility as compared to the device based on pure ruthenium complex.