In this paper，large area CdS thin film was prepared by chemical bath deposition (CBD). The structure and morphology and optical characteristics of the thin film were investigated with XRD，optical transmittance spectra analyzer and AFM. The experimental results indicate that the properties of the thin film were homogeneous. The CdTe solar cells with different thickness of window layer by using the prepared CdS thin film were fabricated. It was found that the short circuit current density，Jsc，of the CdTe solar cells increases with the reduction of the thickness of CdS window layer and the device performance is improved. The module of CdTe solar cells with substrate size 30cm×40cm and total area of 993.6cm2 was fabricated. The results showed that the electrical behaviors of the 27 interconnected unitc were homogeneous too. The efficiency of greater than 8% for the module of CdTe solar cells with area of 993.6 cm2 was obtained.