Abstract: Energy dissipating fixed cone valve is a fluid device commonly used for dissipation of the excessive flow energy in the inflow, and its performance of energy dissipation depends on its internal structure. To improve the performance of its traditional design, we have installed a perforated annular casing and a perforated cone casing behind its valve core and studied how each energy dissipating component inside the valve of this modification affects the performances. A CFD numerical simulation method was adopted to predict and analyze the flows in the valve passages, and three different internal structures were examined and compared. Hydraulic model tests were conducted to verify the simulations. Results show that the cone core is a dominant component in energy dissipation and the total performance of the valve can be improved by installing a perforated annular casing and a perforated cone casing.