A slot antenna assembly adapted to a metal case is provided in the disclosure. The slot antenna assembly includes a substrate and a metal wire. The substrate includes a first sheet plate and a second sheet plate. The first sheet plate is conductive and is provided with a slot opposite to an opening of the metal case, a size of the slot being less than or equal to a size of the opening. The second sheet plate is not conductive and is connected to the first sheet plate. The metal wire is located on a surface of the second sheet plate to be connected to a feeding signal. A vertical projection of the metal wire on the first sheet plate crosses the slot, and the metal wire and the slot together excite a low-frequency mode and a high-frequency mode.