Abstract: Thallium doped cesium iodide (CsI(Tl)) scintillator films are widely used for their dense micro-columnar structure. In this work, CsI(Tl) films with different thickness were fabricated on monocrystalline silicon substrate and polycrystalline Pt/Si substrate by the thermal deposition method. These scintillator films with different thickness were manufactured under the same process conditions and prepared for experiments. The microcrystalline column structures were different during the thickness of films. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the crystal quality and microcrystalline column morphology. The microstructure model of the CsI(Tl) film was built to illustrate the influence of the interplanar spacing on microcrystalline column structures of the monocrystalline film.