Nano-CdS crack-free thin films were deposited on the conductive glass substrate with a two-electrodes DC electrochemical deposited method at low temperature (<100°C). The structure and properties of thin film catalysts were characterized by X-ray diffraction (XRD), SEM and AFM. Photocatalytic reactivities of nano-CdS thin film were conducted for removal of Rhodamine B (RB) in aqueous solution under ultraviolet light irradiation. The effect of the concentration and pH of the RB solution, the ultraviolet light, the exposure time, the size and the reusability of thin films on the degradation of RB were studied. It was found out that the exposure time, the light wavelength, the pH of RB solution and thin film’s size have much influence on the degradation. Reusability experiments show that the catalyst has well recycle characterization.