In view of the frequent occurrence of unsafe problems in homestay inn, this paper proposes a design of fire and theft intelligent alarm system based on single chip microcomputer. The central processor is STC89C52 single-chip microcomputer, and the hardware includes DS18B20 temperature sensor, MQ-2 smoke sensor, human pyroelectric infrared sensor, SIM800C communication module, and LCD1602 display module. The indoor security information is collected by the sensor. If there is an alarm in the room, the alarm device will send an audible and visual alarm under the control of the single-chip computer, and send the indoor alarm to the monitoring center or the customer's mobile phone through the GSM communication module. After receiving the short message, you can request the third party's support through the voice call, thus effectively realizing the purpose of security alarm. The experiment shows that the design of this system has high cost performance, high accuracy, easy installation and operation, and can meet the security needs of small areas such as residential accommodation, which has certain practical significance.