Cadmium sulfide quantum dots (CdS QDs) are widely used in solar cells, light emitting diodes, photocatalysis and biological imaging because of their unique optical and electrical properties. However, there are some drawbacks in existing preparation techniques of CdS QDs, such as protection of inert gas, lengthy reaction time, high reaction temperature, poor crystallinity and non-uniform particle size distribution. In this study, we prepared CdS QDs by liquid phase synthesis under ambient room temperature and atmospheric pressure using sodium alkyl sulfonate, CdCl 2 and Na 2 S as capping agent, cadmium and sulfur sources respectively. The technique offers facile preparation, efficient reaction, low-cost, and controllable particle size. The as-prepared CdS QDs exhibited good crystallinity, excellent monodispersity and uniform particle size. The responsivity of CdS QDs based photodetector was greater than 0.3 μA/W, which makes them suitable for use as UV detector.