An auxiliary material used in an electronic device is provided. The auxiliary material includes an adhesive layer, a foam layer, and a double-sided tape layer that are sequentially stacked, the auxiliary material is used to be bonded between a rear housing of the electronic device and a functional component of the electronic device, the adhesive layer is used to be bonded to the functional component, the double-sided tape layer is used to be bonded to the rear housing, and adhesive force of a surface on which the adhesive layer is bonded to the functional component is less than adhesive force of the double-sided tape layer. An electronic device is provided. A speaker box of the electronic device has a design of an open rear acoustic cavity. The electronic device further includes a rear housing, a functional component, and an auxiliary material. The auxiliary material has a weak-adhesion surface and a strong-adhesion surface that are opposite to each other, adhesive force of the weak-adhesion surface is less than adhesive force of the strong-adhesion surface, the weak-adhesion surface is bonded to the functional component, and the strong-adhesion surface is bonded to the rear housing. A rear housing assembly is provided, and includes a rear housing and an auxiliary material bonded to an inner surface of the rear housing.