This humidity alarm detector is an automatic humidity detector designed for civil application, which adopt 9V battery as the power supply to increase the safety coefficient. It uses the conductivity of water of the alarm source. It consists ot gold-plated probe, signal process circuit and Motorolla special IC. When the humidity reaches designated threshold value, the metal probe transfers the detected signal to internal circuit, which generates the micro current. The micro current will generate the alarm signal after it has been amplified; Therefore the purpose of alarm is achieved.