The invention relates to release films, in particular to a release film and a preparation method thereof. In order to solve the problem that the conventional release film can only be used once, the invention provides a release film and a preparation method thereof. The release film comprises a five-layer structure, and comprises an upper surface layer, an upper buffer layer, an intermediate layer,a lower buffer layer and a lower surface layer from the upper part to the lower part in sequence. The release film is excellent in release property when being applied to manufacture of flexible printed circuit boards, excessive glue of the buffer layer is little, and the release film can be changed with the surface structures of different circuit substrates, so that overflowing of an adhesive layer between a substrate of a circular board and a surface layer covering film of the circular board can be prevented; in addition, the performance of the release film can be recovered after the releasefilm is used once, and the release film can be reused.