Cadmium sulphide (CdS) nanoparticles were chemically synthesized using reverse micelles microreactor methods. By using different washing treatments, UV-Vis spectroscopy showed that the absorption peaks appeared at 465 nm, 462 nm, 460 nm, and 459 nm respectively for CdS nanoparticles without and with 1, 2, and 3 times washing treatments using pure water. In comparison with the absorbance peak of bulk CdS at 512 nm, the shifted absorption peaks, indicates that the different sizes of CdS can be prepared. Anodic stripping voltammetry of the CdS nanoparticles was then studied at a boron-doped diamond electrode using 0.1 M KClO4 and 0.1 M HClO4 as the electrolytes. A scan rate of 100 mV/s with a deposition potential of-1000 mV (vs. Ag/AgCl) for 60 s at a potential scan from-1600 mV to +800 mV (vs. Ag/AgCl) was applied as the optimum condition of the measurements. Highly-accurate linear calibration curves (R2 = 0.99) in 0.1 M HClO4 with the sensitivity of 0.075 mA/mM and the limit of detection of 81 μM in 0.1 M HClO4 can be achieved, which is promising for an application of CdS nanoparticles as a label for biosensors.