Abstract: As a major grain production and consumption country, research on safe storage of grain in China is of great significance．Main parameters affecting grain storage are temperature and humidity, and good control of temperature and humidity in granary can improve quality of safe grain storage．Taking STC89C52 single chip microcomputer as a control unit, and cooperating with DHT11 temperature and humidity sensor, LCD1602 LCD screen, and SIM800L SMS module to manually adjust upper and lower limits of temperature and humidity according to on-site situation．Detected temperature and humidity were displayed in real time on LCD screen and compared with upper and lower limits of temperature and humidity．If limit was exceeded, an alarm would be triggered and a short message would be sent to remind administrator．Through experimental verification, model could manually adjust upper and lower limits of temperature and humidity requirements．When temperature and humidity met requirements, LCD screen would display current temperature and humidity information of granary in real time．When temperature and humidity did not meet requirements, system would issue three alerting modes to administrator: buzzer, warning light, and short message, to handle them promptly．