In the fluid transmission control system, the control valve is used to control the movement and speed of the actuator by manipulating the flow direction, pressure and flow rate of the fluid. The spool valve utilises the relative movement of the spool and the valve body to turn on and off the oil circuit, or change the direction of the fluid flow. The actuator can then be started, stopped or reversed. In this work, the control characteristics of the pressure flow were investigated based on computational fluid dynamics (CFD). By simulating the three-dimensional flow field, the pressure-flow characteristics were analysed at different valve port openings. The design of the valve was optimized to avoid the cavitation phenomenon at the valve port. This work provides a theoretical basis for the research, development and optimization of multi-way valves and the performance improvement of hydraulic systems.