SnS is a promising p-type semiconductor material for low-cost and low-toxic solar cells due to its exciting properties, such as high absorption in the visible range, little toxicity, inexpensiveness, and so on. The CdS nano-layer used as buffer layer of ZnO nanowire arrays/CdS/SnS thin film solar cells was prepared by thermal evaporation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), UV-Vis spectra, Hall effect measurement system and I-V measurement system were used to characterize the ZnO nanowire arrays/CdS/SnS thin film solar cells. It is found that the CdS nano-layer plays a key role in reducing the leakage current.