The invention belongs to the technical field of macromolecule material and macromolecule synthesis, in particular to the preparation for a bisphenol-A polyimide film by adopting the vapor deposition polymerization method. The method for preparing polyimide is characterized in that the bisphenol-A anhydride and the diamine monomer are sublimed in vacuum, which are ploymerized in the process of vapor deposition. The polyimide which is prepared by such method not only can keep the good thermal stability and chemical stability of the polyimide that is prepared by the traditional method, but also can overcome the shortcomings of the traditional method, the polyimide film prepared by such method has the advantages of uniformity and densification, no need of pin hole and catalyst, no solvent residue, high purity and simplified reaction steps.