Water-dispersible CdS quantum dots (QDs) were synthesized in a simple one-pot noninjection route. The X-ray diffraction (XRD) pattern of the nanoparticles shows the cubic structure with particle size of the order 5-7 nm which was in good agreement with the transmission electron microscopic (TEM) studies. Selected area electron diffraction (SAED) recognized the cubic structure of CdS. The energy dispersive X- ray spectroscopy (EDAX) analysis confirms the presence of Cd and S elements in the samples. The optical properties are characterized by Ultraviolet-Visible (UV-Vis) absorption and Photoluminescence (PL) spectra. The synthesis parameters of this simple and rapid approach, including the reaction temperature and time, the pH of the reaction solution and the molar ratio of the 3-mercaptopropionic acid (MPA) stabilizer to Cd 2+ , have considerable influence on the particle size and photoluminescence of the CdS quantum dots. The 3-mercaptopropionic acid (MPA) stabilized CdS QDs can be used in solar cells, light emitting diodes, biological imaging etc.