MCU-based PM2.5 smoke alarms designed home Abstract: With the increase of modern industrial pollution, automobile exhaust emissions, concentrations of PM2.5 is more and more high. For the particle size in the more and more fine particles 2.5 microns or less, smoke detectors have also been used in various occasions. This design is the use of microcomputer with the sensor technology development and design of the smoke alarm system. The main thesis of the smoke alarm system for the various components are introduced, its control circuit and peripheral equipment circuit interface between technology and software have been the focus of introduction. Keywords: Alarm; 80C51; Smoke sensor