Abstract: Flow characteristics in the process of switching one centrifugal pump to the other was investi-gated experimentally using a closed loop with two centrifugal pumps and two check valves.Characteristics of the check valves responding and the flow rate changing during the process of switching was studied by ex-perimental data analysis.The results show that in the switching process with high and low original flow rate,the restoring time is 26s and 21s respectively;the lowest flow rates are 59.4% and 87.2% out of that in normal water supply,and the average deficit of feed water is 20.8% and 7.5% respectively.Compared to double-pump switching with low flow rate,a longer transition time,more intense flow fluctuations and increased water loss are observed with high flow rate,which has significantly effects on the stability of water supply.