Polycrystalline lead iodide (PbI2) thin films have been prepared on glass substrates by vacuum evaporation. The influences of evaporating rate，the distance between the resources and the substrates，the thickness of the films and the temperature of the substrate on the structure of the film were studied. The structures of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results shows that the films were (001) preferentially grown，when the substrate was at room temperature. At higher substrate temperature，the films were mostly (003) preferentially grown and the size of the grains were larger. The internal stress became smaller when the substrate temperature became higher.