At present

the temperature of working water in water-ring vacuum pumps is often higher than the designed value

and the said temperature hasn't been unitfiedly determined.Under condition of considering the influence of variable operating condition for the condenser

the steam resistance in condenser

the resistance of air-extracting pipe

and evapouration of working water in water-ring vacuum pump

and under prerequisite of satisfying requirement for ensuring air-extracting capability from the condenser

a method for detemining maximum temperature of working water in the water-ring vacuum pump for keeping vacuum in the condenser has been given

providing with basis for optimizing operation of the water-ring vacuum pumps.