Abstract: The experimental and numerical studies on the flow resistance characteristics under flow fluctuating conditions in a circular channel are carried out.The experimental results show that the pressure drop fluctuates with the same period of fluctuating flow rate;however,there is a phase lag between the two,and the phase lag in laminar flow is bigger than that in turbulent flow.In addition,the flow characteristics under the experiment conditions are numerically simulated based on the method of characteristic（MOC）.The simulation results are in agreement with experimental values.