Abstract: This paper introduces an automatic protection and control system for the boiler drum water level of a centralized heating boiler, based on a Siemens S7-200 series programmable logic controller (PLC). The paper first discusses the principle of boiler drum water level control, presents a suitable control scheme, the system's hardware configuration and software design, proposes a scheme for remote monitoring and control using the CP243-1 module, and provides a detailed introduction to the main instrument, the Siemens S7-200. The system has a robust and user-friendly interface, fully meeting operational requirements. Keywords: Programmable Logic Controller (PLC); Boiler; Water Level Protection; Remote Monitoring In the past, large-scale centralized heating boiler room control systems commonly used relay and contactor control circuits, which had simple control functions and certain shortcomings in reliability and optimized control. With the advent of the Programmable Logic Controller (PLC), it has challenged traditional control methods with its outstanding advantages. The boiler drum water level protection and control plays a crucial role in the entire system. Maintaining the boiler drum water level within a certain range is a necessary condition for ensuring the normal operation of the boiler during centralized heating boiler operation. The water level protection function should ensure timely protection when the boiler is short of water, preventing dry-boil and damage to the water-cooled walls. It should automatically open the drain valve when the boiler is full of water. When the water level reaches its limit, it should shut down the boiler, stop the machine, and close the main steam valve to prevent equipment damage. We use a Siemens S7-200 PLC in the centralized heating boiler drum water level protection system. The working principle of the entire centralized heating boiler drum water level protection system is as follows: A pressure sensor detects the boiler drum water level. The received standard 4-20 mA or 0-5 V signal is sent to the field control unit (PLC) via a signal conditioning module. After intelligent processing, a control signal is generated and then sent back to the field execution unit (solenoid valve) via the signal conditioning module. This controls the boiler. Simultaneously, the control units are connected via Ethernet, sending the signals to be monitored to the host computer for human-machine interaction and remote monitoring. For details, please click: PLC-based centralized heating boiler drum water level protection control.