Abstract: This paper introduces the architecture and functions of the Xihe Gate Control System in Chongzhou City, Sichuan Province, and presents the system design scheme, hardware wiring diagram, and software programming flowchart for PLC implementation. Keywords: PLC, Gate Control, OMRON CompoBus/S The Xihe Dam in Chongzhou City, Sichuan Province, consists of 17 gates. Its span is approximately 300m, and the maximum gate opening is 1.7m. The gate control room is 40m from the upstream side of the dam. Due to the large geographical span, this gate control system adopts a bus-based distributed hierarchical control design. 1 Architecture and Working Principle of the Xihe Gate Control System The Xihe Gate Control System adopts a bus-based distributed control method, divided into two levels: field control and centralized control. The bus adopts the OMRON CompoBus/S fieldbus protocol, as shown in Figure 1. The field level consists of 17 gate control cabinets (CPU using OMRON CP1H series PLCs) installed at each gate. Its functions include enabling manual control of the gate on-site, collecting and monitoring water level, gate opening, gate operating status, and error information, and completing real-time communication with the centralized control level, including receiving control information, performing gate control actions, and sending gate operating status and error information for remote monitoring to the main station. The centralized control level consists of a control cabinet (using an OMRON CJ1G series PLC) located in the gate control room. Its main functions are: communicating with lower-level systems via CompoBus/S, processing relevant data, sending gate operating status and error information to the monitoring host, and forwarding instructions from the monitoring host downwards. The monitoring host receives and displays gate opening, status, and other information through monitoring software (KingSCADA in this system), alarms for error information, and can issue instructions to control gate operation, while also generating reports. A UPS power supply is used to power both levels of the control system during power outages, ensuring uninterrupted system operation. For details, please click: Development of the Xihe Gate Control System Based on PLC and Fieldbus.