The hollow jet valve is a special type of needle valve which is usually established at the end of the spill way in a dam of a hydroelectric power station or a large-scale water transportation system. The working condition of this valve is usually under a high head and high discharge capacity, so that the structure of valve has to be strengthened. In addition, the capacity controlled process can cause cavitation which produces cavitation noise, vibration and erosive damage. Cavitation can affect strongly on the lifetime of valve and the safety of system. Thus, so many research works have forcused in flow dynamics around the hollow-jet valve. In this paper, the 3-D flow field of a hollow jet valve is simulated and analyzed by CFD tool. The effect of the defined parameter - opening coefficient Beta to the hydraulic characteristics is analyzed and estimated. Comparing to the experimental observation, the induced vortex cavitation area around the valve needle body is clarified by the jet flow separated from the needle edge. Additionally, the specification of the valve is also predicted in the diferent opening coefficient Beta for studying of valve working control and engineering application.