CsI films were prepared on glass substrates by thermal evaporation and annealed under various tempera- ture.Structure and scintillation properties of films were examined using X-ray diffraction

scanning electron micro- scope and scintillation pulse height spectrometry.The results show that the crystalline structure and scintillation properties of the CsI films depend on the annealing temperature.The samples annealed at 250℃have a good crystal- line state and scintillation properties.As the annealing temperature goes up to 400℃

the light output of samples de- creases seriously.