A method of controlling the recirculatary valve for minimum flow rate of feed-water by using the hysteresis function method has been put forward for preventing occurrence of cavitation in feed-water pumps.The comparison of said method with the commonly used control method in engineering

namely single curve method

and with the PID regulation-controlling method

as well as the practical application show that the method of controlling the recirculatory valve for minimum flow rate of feed-water pumps by using the hysteresis function method is more reliable and effective in prevention of cavitation in feed-water pumps.