In this fire alarm system, the AT89S51 single chip microcomputer is used as the main control core, the DS18B20 temperature sensor collects temperature information, and the MQ-2 gas sensor is used to collect gas information.The data collected by the DS18B20 is a digital signal that can be sent directly to the MCU for processing, and the signal output from the MQ-2 gas sensor is an analog signal that is converted to a digital signal with an analog-to-digital converter and sent to the MCU for processing. .The alarm threshold is preset in the internal program of the single-chip microcomputer, including high temperature alarm and high gas concentration alarm, and it is judged whether the received data has reached the alarm threshold after the single-chip microcomputer is operating normally. The LED light alarm will continue to receive and process new data if the alarm value is not reached.