In this paper, the effects of different concentrations of complexing agent (ammonia) on the surface morphology, composition, structure and photoelectric properties of CdZnS films were studied. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible spectrum showed that the surface morphology of the films became worse and the content of zinc decreased significantly with the increase of ammonia concentration. The crystalline phase of CdZnS films was not influenced by the ammonia concentration. Because the film has good absorbance, transmittance greater than 70% and band gap width between 3.5 eV and 3.07 eV, it is suitable to be used as a buffer layer for solar cells. CdS, ZnO and Zn(OH)2 were found in the precipitates at the bottom of the solution, and the formation of these precipitates affected the properties of the CdZnS films.