Abstract: The automatic and real-time irrigation system based on estimation of water stress in crops with acoustic emission (AE) technology was developed. Taking the tomato crops as a testing example in greenhouse, the system can acquire the real-time AE signals and transpiration data respectively through AE sensor and electronic balance, and the computer program of an optimum algorithms for the irrigation system was also produced based on the AE signals and transpiration data. It shows that the AE events increase gradually with the increase of transpiration speed of crops to some extent. In order to keep the crops growing well, it has the potential to indirectly detect and monitor the water stress in tomato crops based on the information acquired from the crops through AE and transpiration.