Based on the lift and pipe characteristics of a water supply system, the energy-saving effects of frequency conversion control and valve control were analyzed and applied in water-saving irrigation system. The traditional method to adjust the valve opening and to turn on or turn off the pump engine by people to meet the need of water supply was improved. It has the energy-saving effect of 20%～69%, but also has the benefit in prolonging the service life of equipment, improving the stability of water amount and water pressure and reducing human errors in their operation. The control of a water supply system by frequency conversion are realized.