The nanocrystalline CdS was prepared by the two methods, thermal decomposition using autoclave about 300degreesC and by gamma-radiation at room temperature. Cd(oleate)(2) solution was used as the cadmium ion sources. Na2S.9H(2)O was used as the S sources. X-ray Powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structure and to observe their morphology and size of produced CdS nanoparticle, respectively. The photoluminescence (PL) spectrum was obtained to characterize the optical properties of CdS nanoparticle.