The invention discloses a prefabricated building wall, and relates to the field of building. The wall is composed of a plurality of wall units, and a first connecting part and a second connecting partare respectively arranged at the left side and the right side of every wall unit; the second connecting part of every wall unit can be embedded in the first connecting part of the adjacent wall unit,and a ventilation gap is formed between the first connecting part and the second connecting part; an air duct is arranged to communicate with the ventilation gap; an inner chamber is arranged in every wall unit, one side surface of the ventilation gap is provided with an opening communicated with the inner chamber, and is provided with an elastic layer for sealing the opening; a pressurizing chamber is arranged below the inner chamber, a first piston is slidably connected in the pressurizing chamber, a first non-return valve is arranged to communicate the pressurizing chamber with the inner chamber, a second non-return valve communicates the pressurizing chamber with the outside, a pressure spring is arranged below the first piston, and the first piston is fixedly provided with a floor suspension; and a pressure release valve for releasing the pressure of the inner chamber is arranged. The wall is easy to assemble and disassemble, has a good ventilation effect in summer, and has a good warming effect in winter.