A frame includes a first frame, a back case and a second frame. The first frame includes a first frame plate and a first frame wall, the back case includes a back case plate and a back case wall, the second frame includes a second frame plate and a second frame wall, and the second frame surrounds the first frame and the back case. The second frame plate is located on a side of the first frame plate facing away from the back case plate, and the first frame wall is protruded from a surface of the first frame plate facing towards the back case plate, the back case wall is protruded from a surface of the back case plate facing towards the first frame plate, and the second frame wall is protruded from a surface of the second frame plate facing towards the first frame plate.