Abstract: In order to precisely determine the extent of the water deficit and thus to provide a scientific reference for the precision irrigation, a wireless sensor networks (WSNs) node was designed and a particular design of WSNs precision irrigation system (WSN-PI) is proposed based on the acoustic emission technique for crop water stress. The designed WSN-PI system enables usere to precisely acquire the crop water requirement information and thus to implement the precision irrigation at any time and everywhere. It possesses many advantages, such as low energy consumption, inexpensiveness, good robustness, flexible extensibility, etc. Preliminary experimentations indicate the rationality and practicability of the system. It can be effectively applied to the greenhouse, the cropland, and the nursery garden, etc. This research contributes to the exploration on the applications of WSNs in water-saving agriculture.