The invention discloses a device and a method for detecting an insulator fault based on air heat striation distribution. The device comprises a light source module, a striation acquisition module consisting of a striation mirror, a second reflecting plane mirror, a knife unit and a photosensitive board, a data processing module and a computer. By the method, whether an insulator is normal is judged by calculating whether a comprehensive similarity value between an acquired normal working curve of the insulator and an acquired working curve of an insulator to be detected is greater than a preset threshold. The comprehensive similarity value considers the similarity and the distance between the normal working curve of the insulator and the working curve of the insulator to be detected. The method is intuitive and reliable; by the method, manpower and material resources can be saved; the method has a relatively large practical application value in engineering.