The application of alarm systems is very extensive, and alarm circuits are almost invariably used in car and motorcycle alarms, warehouse doors, and home security systems. With the rapid development of social science and technology, people have put forward increasingly high requirements for the performance of alarm devices. Traditional alarm devices usually use touch sensitive, on/off alarm devices, etc. This type of alarm has the characteristics of stable performance and strong practicality, but also has the disadvantage of narrow application range. And the security performance is not very good either. The photoelectric alarm has greatly improved this point. Nowadays, photoelectric alarms have been widely used in industrial and agricultural production, automation instruments, medical electronic equipment and other fields. The design of this experiment utilizes analog circuits and digital logic circuits, adopting a modular design concept, making the design simple, convenient and flexible. The circuit is simple, easy to implement, and works stably, so it has been widely used.