A cover assembly includes a housing plate and a cover. The housing plate includes a first wall, a second wall, a third wall, and a fourth wall. The housing plate defines a rectangular opening. The first, second, third, and fourth walls are formed at the four edges of the rectangular opening. The housing plate defines a first positioning slot in the first wall, two second positioning slots at one end of the second wall and the third wall adjacent to the first wall, and a third positioning slot at a side of the rectangular opening. The cover includes a front end, an opposite rear end, a first locking sheet on the middle of the front end, two second locking sheets on both sides of the front end, and two third locking sheets on the inner surface of the disassembly portion and protruding from the rear end to the front end.