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 (WSN) node was designed and a particular design of WSN-based crop precision irrigation system (WSN-CPI) was proposed based on the stem diameter microvariation diagnosis method for water stress. The designed WSN-CPI system enables users to precisely acquire the crop water requirement information and thus to implement the precision irrigation at any time and anywhere. 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 greenhouse, cropland, and nursery garden, etc. This research contributes to the exploration on the applications of WSN in water-saving agriculture.