The utility model discloses a water falling device for a two sections type closestool water tank , which is composed of a water falling pipe, a water stopping valve, a first pulling rope and a second pilling rope; and the bottom of the water falling device has an air groove the lateral end of which has an air releasing hole. The water falling device for the closestool water tank is characterized in that the top protruding ear of the water stopping valve is pin jointed with one end of a rocking rod and the other end stretches toward the rod body of the water falling pipe. The first pulling rope is connected with a lifting water stopping valve that can pull the rocking rod to upwardly rotate on the rocking rod. When pulling the first pulling rope, the rocking rod rotates upwardly to stray away the water falling rod and to completely lift up the water stopping valve, the water valve falls in advance due to that the air inside the air groove is quickly released out, with the water falling cut being sealed. When pulling the second pulling rope, the water stopping valve can not be completely lifted up to reducing the releasing speed of the air, and to stop the water stopping valve from falling in advance by making the end part of the rocking rod touch closely to the water falling rod body. The water falling cut is not sealed until the water inside the tank is completely released out.