Hydraulic water level control valve has the function of automatically opening and closing pipes to control water level. It is suitable for industrial and mining enterprises and various water tower (pool) automatic water supply systems in civil buildings. It can also be used as circulating water supply control valve of atmospheric pressure boiler. The valve is small in size, easy to install, high sensitivity to start-up and small water head loss without water hammer. The utilization ratio of water tower can be greatly improved by using small float ball control. Because the volume of floating ball is reduced, the height of floating ball left to the upper part of the water tower is reduced and the water tower medium is reduced. It overcomes the disadvantages of the old rod floating ball valve, such as large volume, easy damage, low working pressure and large amount of overflow. It is more appropriate to build a new water tower and replace the old floating ball valve.