Inordertostudytheflowcharacteristicsofthering-jetflowcontrolvalve， takingthe DN900ring-jet regulating valve as an example， the local energy loss analysis method isused to divide the flow-through part into three parts.There are results of flow resistancecoefficient and the flow coefficient and head loss of ring-jet valve under the 50mnet waterhead by theoretical calculation with different opening degrees.The numerical analysis meth-o disused to get flow resistance coefficient and flow coefficient and head loss under the samehead， at the sametime internal flow characteristics of the valve are analyzed.By comparingthe results calculated by two methods， it is shown that the flow resistance coefficient basedon local loss derivation andnumerical calculation has the same distribution law，and itgrows rapidly with the decrease of opening degree.The calculation results are in good a-greement with large opening degree.There is a vortex when the fluid flows through thevalve.In order to improve the cavitation of the valve， a gas supplement can be added to thevalve.