Abstract: The method of changing the internal flow characteristics of the control valve by using an internally-cut control valve spools structure is proposed to solve the problems of unstable operation, vibration, and abnormal noise in a certain type of turbine unit. Methods By utilizing the full-scale high-precision modeling approach, the complete flow area of a specific type of control valve is established. Two types of internally-cut control valve spools were designed based on the principles of supersonic expansion suppression. The grid division method employs a multi-scale hybrid grid and multiple types of boundary layer grids. Accelerated convergence is achieved through multiple iterative calculations. Results The final computational results showed less than 5% error compared to experimental measurements. The simulation analysis indicates that the new internally-cut valve enhances steam flow performance in the throttle area and at the base of the valve spool. This optimization helps reduce energy loss and vibration noise caused by asymmetric flow beneath the spool. Additionally, the new spool structure reduces the steam's force on the control valve by 20% to 30%.Conclusions The structure of the control valve spool significantly influences the characteristics of the flow field. The design of the internally-cut control valve spools offers valuable guidance for optimizing flow field distribution.