The present invention provides a method for designing USB floating with low electromagnetic interference, especially in a scenario in which a distance between a pin and a metal housing of a USB interface of a terminal device is increasingly small. A first plug and a second plug are connected by using a connection cable having a first shield layer and a second shield layer. The first shield layer and the second shield layer overlap and there is no electrical connection between the first shield layer and the second shield layer. One end of the first shield layer is connected to a metal housing of the first plug, and the other end is suspended. One end of the second shield layer is connected to a metal housing of the second plug, and the other end is suspended. In addition, a metal housing of a first socket and a metal housing of a second socket may be connected to a housing of the terminal device or a housing of an adapter by using a capacitive component, thereby helping the terminal device reduce a short circuit risk and radiation.