A breeding cage for experimental animals is composed of a box body and a cover body covered with the box body. A side of the cover body is disposed with an air intake valve and an air vent valve. A partition is disposed in the cover body to allow an inside of the cover body to define a drainage channel. Fresh air enters from the air intake valve and is then downwardly introduced into the box body through the drainage channel and pushes air originally within the box body to exhaust it away from the air vent valve to allow air within the box body to perform circulation.
