Colloidal CdS stabilized with (NaPO3)6 was prepared from Cd(NO3)2 and Na2S. The precursor of poly(p-phenylene vinylene), PPV, was synthesized through Wessling's route. PPV precursor/CdS multilayer films were fabricated via the layer-by-layer electrostatic self-assembly technique. After thermal treating the PPV precursor/CdS films, PPV/CdS nanocomposite films were formed. The colloidal CdS and the composite films were characterized using a UV-vis spectrophotometer and a fluorescence spectrophotometer. A photoluminescence peak of the PPV/CdS multilayer film appears at around 380 nm, suggesting that the photoluminescence of the composite films should attribute to the CdS nanoparticles. The electroluminescence spectra show that a strong luminescence band appears in range 350~650 nm, centering around 530 nm, suggesting that the electroluminescence of the composite films should mainly attribute to PPV. For the ITO/(PPV/CdS)20/Al device, the threshold voltage was about 5 V, and the luminescence intensities increased as the biased voltages increased. In the PPV/CdS nanocomposite film-based light emitting device, CdS plays a role mainly in electron-transporting and PPV works mainly in electroluminescence. However, at higher voltages, CdS nanoparticles may also emit light.