The invention provides a method for preparing [CuIn (SSe) 2] films and belongs to the technical field of preparation of film solar cell materials and the non-vacuum coating film preparing process. The method includes: firstly, preparing oleylamine-coated monodisperse CuInS2 nanocrystalline; secondly, using pyridine for replacement of oleylamine molecules on the surface of the nanocrystalline and dispersing into chloroform or toluene; thirdly, performing film coating on molybdenum coated glass; and finally performing selenizing and annealing treatment for a CuInS2 nanocrystalline film by a solid-state selenium selenization method to prepare a large-grained CuIn (SSe) 2 film. The large-grained CuIn (SSe) 2 film can be obtained by the method. The method for preparing the CIS [CuIn (SSe) 2] films is simple in process, can be massively prepared and is cost-saving.