The nanometer CdS-sulfonic group polyaniline (SPAn) polymer multiplayer films were grown in self-assembled layer-by-layer is reported and the optical properties are investigated. The optical measurement results show that the quantum size effect becomes strong with the decrease of the size of CdS nanocrystals. Blue shift appears on the absorb edgea in the absorption spectrum and also on the exciton band-edge emission peaks in the luminescence spectrum. The observed results of the corresponding annealed samples show that the intensity of the band-edge emission from the exciton direct recombination canbe enhanced about two to three times, and the band width becomes narrower than that of the un-annealed sample， indicating that CdS nanocrystals become more ordering, and their sizes become more uniform in the annealed sample.