Serious seepage can influence the stabilization of reservoir dam and accessory structure. In order to monitor the seepage phenomenon of Wohu-Mountain reservoir exactly at real-time, automatic monitoring system for earth dam is developed. For the hardware system, sensors on site and control computer in center control station are connected effectively with four-core cable, data acquisition device and signal conversion equipment. For the software system, advanced hierarchical and distributed structure is adopted in the system to manage and control monitoring sensors. By developing the data base, seepage curve and related analysis can be shown on the system at real-time. And if monitoring data surpass the limited value, the warning information will be given by adopting different ways according to alarming grade. In general, the automatic monitoring system can play an important role in the protection of the safe of reservoir, and exert economic and social benefits of water reservoirs at mostly.