The water alarm is an automatic humidity detector which is for household appliances. It uses 9V battery as its power supply to increase the safety performance. The alarm consists of sensor, signal processing identification circuit and alarm circuit. It uses water's conductivity as its alarm signal source. If humidity reaches a certain value, the detected signal will be trasmited to intrenal ciruit by the probes. The internal circuit generates micro-current which will generate alarm signal after being amplified, accordingly the purpose of alarming is acchieved. Put it where water may seep, such as at home or in the restaurant, hotel, kitchen, bathroom and so on. The product has a special design, modern and fashion, small and artistic, and is of convenience to use.