CdS nanoparticles were synthesized in polymer networks. EDAX data show that the content of Cd2+ was about 3%wt. The particles size can be controlled by varying the amount of H2S, and the absorption spectra indicated that the band edge shifts toward blue with decreasing the particles size. TEM and diffraction data show that the CdS nanoparticles with narrow size distribution were well assembled in polymer networks, and it has a hexagonal structure.