In this paper, we reported on an approach to prepare tin disulfide (SnS2) thin films on soda-lime glass substrates by vacuum thermal evaporation using SnS2 powders as a source. The influence of annealing on the chemical composition, crystal structure, surface morphology, and optical band gap of the SnS2 thin films was systemically investigated. The as-grown SnS2 thin film was amorphous, homogeneous, smooth, nearly stoichiometric, with no pinhole and crack free, and with an optical band gap of 2.41 eV. After the SnS2 thin film was annealed at 300 degrees C, the crystallization of SnS2 was demonstrated by X-ray diffraction and scanning electron microscope with a characteristic of a preferred orientation along (001) plane with hexagonal phase and the sheet appearance of the SnS2 crystals. At the annealing temperature of 350 degrees C, some SnS2 crystallites and a few pinholes appeared on the surface of the SnS2 thin films, though the SnS2 thin film was not oxidized. When the annealing temperature was increased to 400 degrees C, SnS2 was gradually oxidized into an approximate spherical shape of SnO2 from the top to the bottom of the SnS2 thin film by trace O-2 in the furnace. Therefore, our experiment suggested that the annealing temperature of the SnS2 thin film using the vacuum thermal evaporation should not be over 300 degrees C as a window layer in compound thin film solar cells. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.