In this article,CdS thin films were deposited on glass substrates by chemical ba th deposition (CBD) technique,and the influence of solution PH value on structu ral properties of CdS thin films is researched.The thickness,the composition,the crystal structure and the morphology of the films were measured by step Meter,X-ray diffraction (XRD) and scanning electron microscope (SEM),respectively.The cryst al phase of CdS thin films is mainly hexagonal phase for smaller PH values (for 11.26, 11.37and 11.48),and the thickness of the films first increases and then decreases.The crystal phase of CdS thin films is mainly cubic phase for higher PH values (for 11.62and 11.66), and the thickness of the films is further reduced.The crystal lattices of CdS thin films gradually increase with the inc rease of solution PH values. When the heterojunctions are formed by CIGS thin films and CdS thin films with two different crystal phases n(hexagonal phase and cubic phase),the crystal mismatches are res pectively 32.297%(hexagonal phase) and 1.419% (cubic phase),and the interface state dens ities are respectively 2.792×10¹⁴ (hexagonal phase) and 8.507×10¹² (cubic phase).Therefor e,it is more necessary to deposit the cubic phase CdS thin films for high efficiency CIGS thin film solar cells.