由于聚酰亚胺分子链的刚性，在成膜过程中，其分子链沿膜平面排列（取向），构成了各向异性，导致膜平面方向与垂直于膜平面方向的物性参数（如折射率、介电系数）不相同。文中总结了各种研究聚酰亚胺膜各向异性的方法，证明聚酰亚胺膜具有各向异性。 Due to the rigidity of the polyimide molecular chain, the molecular chains are aligned (oriented) along the film plane during the film forming process to form anisotropy, which leads to the physical properties of the film in the plane direction and the direction perpendicular to the plane of the film (such as the refractive index , Dielectric coefficient) is not the same. In this paper, a variety of methods for studying the anisotropy of polyimide films are summarized, showing that the polyimide films have anisotropy.