Abstract: This paper introduces a PLC-based intelligent fire alarm system. By selecting PLC hardware suitable for fire detection, and combining smoke, temperature and other sensors to collect fire signals, a set of signal processing algorithms and logic control strategies based on PLC are designed and developed, which can evacuate and trigger the corresponding fire extinguishing devices and exhaust devices through various methods such as buzzer alarms and light alarms. The system is equipped with an HMI interface that allows managers to monitor and feedback the status of the system in real time. Through network communication technology, the system can be remotely connected with the monitoring center and support remote monitoring and management functions.