In order to obtain the fluid production parameters of each production layer in the wellbore, we designed an intelligent completion downhole multi-parameter monitoring system. This system can acquire key fluid production and control parameters such as the downhole pressure, temperature, water cut, flow rate, and sliding sleeve displacement. It also achieves the function of hydraulic directional control for the downhole hydraulic sliding sleeve. Based on the requirements of parameter monitoring and control, we designed downhole monitoring circuit modules, downhole hydraulic directional control circuit modules, and downhole communication modules, as well as a host computer monitoring platform with corresponding functions. The test results of the system prototype show that 1) this system is able to perform downhole fluid parameter measurement, hydraulic directional control, and bidirectional signal transmission; 2) the surface monitoring platform can receive real-time formation parameter measurement data, ensuring smooth communication for transmitting and receiving commands; 3) the software functions properly, supporting downhole data display, data storage, and motor drive control. Performance tests of the system indicate that it meets downhole environmental requirements and realizes the three major functions of intelligent completion: measurement, control, and transmission. This further improves China’s intelligent completion technology framework.