An autotransformer is a special type of transformer in which the primary and secondary windings are on the same winding. The primary and secondary windings of this transformer are directly connected in series and self-coupled. Autotransformers are widely used in many fields. Next, we will mainly introduce the specific applications of autotransformers in eight aspects, including power systems, industrial automation, test equipment, audio processing, communication systems, railway transportation, measuring instruments, and aerospace.