The microstructure morphology and crystal quality of CsI(Tl) films are influenced by the crystal properties of substrates. In this work, CsI(Tl) films on the glass and single crystal silicon substrates are fabricated by vacuum thermal evaporation at a low deposition rate. The microstructure morphology, crystalline quality and scintillation properties of the films were examined by using scanning electron microscopy, X-ray diffraction, photoluminescence and radioluminescent spectrum. To study the growth mechanism of CsI(Tl) films on amorphous and monocrystalline substrates, a growth model based on the classical Volmer-Weber (VW) growth mode are proposed. During the film growing, the wetting and not-wetting phenomena of the clusters appear on the glass and Si(111) substrates respectively. In addition, the microcrystalline columns with different orientations are modeled to explain the surface morphology deteriorate of the CsI(Tl) film with 3 mu m thickness on Si(111) substrate.