A ball float valve comprises a float, a valve body, a valve flap, a conical sealing gasket and a guide mechanism (or a spacing mechanism), wherein the conical sealing gasket is mounted fixedly on the valve flap assembled on the float, the valve body is provided with an outflow eyelet, the guide mechanism is capable of guiding (or spacing) for the valve flap and enabling the conical sealing gasket to head towards the midst of the outflow eyelet, the ball float valve is provided with a structure that outgoing current from the outflow eyelet does not flow via the top surface of the ball float valve, a water-stop sheet arranged in the internal of the float can divide the float into pluralities of internal cavities for producing buoyancy separately. The ball float valve is mainly used for an one-purpose water purifier of a drinking machine to control the water level of a bucket of the drinking machine, further can be used in other similar occasions. The invention has the advantages that the float of the ball float valve can be adjusted automatically, has a low requirement for guiding (or spacing), and shows considerable improvement of reliability of water stopping of the ball float valve.