Recently, the study of the physical and chemical property of semiconductor nanoparticles (Q-particles) has attracted much attention because of their variety of applicability to nanodevices. In this study, cadmium sulfide (CdS) nanoparticles were prepared by dissolving of cadmium perchlorate hydrate (Cd(ClO4)2ㆍ6H2O) and hexametaphosphate(HMP, (NaPO3)6), hydrogen sulfide (H2S) gas in water and precipitating the ionic crystals. The effects of concentration of Cd(ClO4)2ㆍ6H2O and H2S on the size of CdS nanoparticles were investigated by employing transmission electron microscopy (TEM) and UV-vis spectroscopy. With increasing concentration of Cd(ClO4)2ㆍ6H2O and the particle size significantly increased whereas it slightly did with increasing H2S concentration.